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UNIVERSITY  OF  ILLINOIS 

Agricultural  Experiment  Station 


BULLETIN  NO.  251 


BLOOMING  PERIODS  OF  APPLES 


BY  CHARLES  S.  CBANDALL 


URBANA,  ILLINOIS,  MAY,  1924 


CONTENTS  OF  BULLETIN  No.  251 

INTRODUCTION 11S 

CHARACTER  OF  RECORDS 114 

FLOWERING   PERIODS   VARIABLE H5 

BLOOM  RECORDS  OF  OTHER  LOCALITIES H6 

BLOOM  RECORDS  AT  THE  ILLINOIS  STATION 120 

Full  Flowering  Periods  for  All  Varieties 120 

Early  Blooming  Varieties 122 

Late  Blooming  Varieties 123 

Blooming  Period  of  1910 124 

Comparison  of  the  Periods  for  the  Years  1904  and  1910 126 

Varietal  Flowering  Periods 130 

Amount  of  Bloom 131 

Amount  of  Bloom  and  Distribution  of  Varieties  into  Time-Groups 139 

Temperature  and  Distribution  of  Bloom 140 

Inconstancy  of  Relative  Lengths  of  Varietal  Blooming  Periods 141 

SUMMARY  .  lii 


BLOOMING  PERIODS  OF  APPLES 

BY  CHARLES  S.  CEANDALL,  CHIEF  IN  PLANT  BREEDING  IN  HORTICULTURE 

INTRODUCTION 

The  recording  of  periodical  plant  phenomena  has  received  more  at- 
tention in  recent  years  than  formerly,  and  there  is  now  abundant  evi- 
dence of  general  belief  in  the  scientific  and  economic  importance  of 
data  of  this  character. 

Flowering  of  fruit  plants  in  spring  marks,  perhaps,  the  most 
critical  event  in  the  production  of  a  crop  of  fruit,  and  careful  study 
of  circumstances  occurring  at  that  time,  together  with  an  effort  to  de- 
termine and  understand  the  influences  that  make  for  good  or  bad  re- 
sults, is  deserving  of  attention,  especially  by  those  who  make  fruit 
growing  a  business.  Owners  or  managers  of  orchards  would  derive 
satisfaction  from  annual  records  of  flowering  periods  of  the  varieties 
they  grow,  and  compilation  of  numerous  such  records  would  aid 
greatly  in  understanding  the  influences  that  cause  wide  variations 
from  year  to  year,  but  the  Experiment  Stations  may  rightly  be  ex- 
pected to  maintain  more  complete  and  continuous  records  of  bloom- 
ing phenomena  than  is  usually  possible  for  individuals  because,  once 
started,  the  making  of  such  records  is  regarded  as  a  regular  duty  with 
its  proper  place  in  the  schedule  of  operations,  and  is  maintained  re- 
gardless of  changes  in  personnel.  Many  stations  having  fruit  planta- 
tions now  maintain  such  records  and  each  succeeding  year  adds  to 
their  value.  These  records  have  been  discussed  in  several  valuable 
bulletins,  and  short  accounts  of  work  done  or  in  progress  have  ap- 
peared in  various  station  reports. 

Blooming  dates  and  periods  are  profoundly  influenced  by,  in  fact 
appear  to  be  in  large  measure  dependent  upon,  meteorological  condi- 
tions, and,  as  these  conditions  vary  extremely  from  year  to  year,  long 
continued  records  are  necessary  in  order  to  supply  a  sound  basis  from 
which  to  judge  probable  results  under  varying  combinations  of  im- 
portant influences.  Any  series  of  observations  on  plant  events  is  of 
most  value  for  the  locality  where  made,  but  in  many  features  is  of 
value  over  wide  districts,  which  possess  somewhat  similar  soil  and 
climatic  features.  Surface  features  of  the  country,  as  a  whole,  are  so 
diverse,  and  the  range  of  variation  in  all  those  elements  that  affect 
growth,  flowering,  and  fruiting  of  plants  is  so  wide  that  records  should 
be  kept  at  many  different  points  by  many  observers.  Out  of  the  ag- 
gregate of  such  records  valuable  light  on  the  causes  of  many  phenom- 
ena now  imperfectly  understood,  should  eventually  come. 

113 


114  BULLETIN  No.  251  [May, 

The  purpose  of  this  publication  is  to  give  a  brief  account  of  flower- 
ing records  for  apples  at  the  Illinois  Station.  The  data  to  be  con- 
sidered include  flowering  dates  and  periods  for  106  varieties  having 
records  ranging  from  ten  to  sixteen  years:  the  list  of  varieties  in- 
cludes most  of  those  commonly  grown  in  the  state,  and  also  a  con- 
siderable number  of  Russian  varieties.  The  trees  upon  which  obser- 
vations were  made  were  of  nearly  the  same  age,  and  were  grown  under 
identical  conditions.  Many  varieties  were  represented  by  more  than 
one  tree,  some  by  several  trees,  but  the  records  to  be  mentioned  are  for 
single  individuals  of  each  variety. 

CHARACTER  OF  RECORDS 

Records  have  been  taken  on  forms  prepared  in  advance  and  bound 
in  book  form,  one  book  for  each  year.  Each  page  lists  the  trees  of  one 
row,  numbered  consecutively  according  to  position,  and  is  ruled  in  five 
columns  with  space  allowed  below  for  any  remarks  that  seem  desirable. 
The  numbers  occupy  the  left-hand  column,  followed  by  the  three  date 
columns:  " opening  of  first  flower,"  "full  bloom,"  and  "petals 
falling."  In  the  fifth  column  is  recorded  a  general  estimate  of  the 
amount  of  bloom. 

The  record  in  the  second  column,  except  in  rare  instances,  is  a 
simple  statement  of  fact ;  either  a  flower  was  open  or  was  not  open  on 
a  given  date,  but  cases  of  receptive  stigmas  protruding  before  petals 
had  expanded  were  sometimes  encountered,  and  then  the  exact  day  of 
first  open  flower  was  a  matter  of  question.  This  condition  was  so  rare, 
however,  with  the  varieties  under  consideration  as  to  be  negligible.  In 
some  of  the  crab-like  species  of  the  genus,  notably  in  forms  of  Mains 
floribunda,  Mains  toringo,  and  Mains  microcarpa,  the  maturity  of 
stigmas  was  so  commonly  in  advance  of  expansion  of  petals  that  the 
date  of  first  open  flower  was  often  uncertain.  Records  of  these  crab- 
like  species,  however,  are  all  below  the  ten-year  limit  and  are  not  to  be 
considered  at  this  time. 

Date  of  "full  bloom"  was  often  a  matter  of  judgment  and,  hence 
variable,  especially  in  those  seasons  when  flowers  opened  slowly  be- 
cause of  storms  and  low  temperatures.  The  third  date,  that  of  "petals 
falling,"  not  infrequently  was  a  matter  of  judgment  and  subject  to 
fluctuation  and  error.  Suppose  that,  following  the  opening  of  a  few 
flowers,  a  change  in  weather  suspended  plant  activities  for  three,  four, 
or  more  days,  this  being  followed  by  high  temperatures  and  rapid 
opening  of  flowers.  Under  such  circumstances  the  petals  of  the  first 
flowers  open  would  fall  before  the  date  of  full  bloom  was  reached.  It 
was  assumed  that  the  date  to  be  recorded  should  apply  to  the  mass  of 
flowers  rather  than  to  the  few  precocious  individuals,  but  cases  have 
occurred  in  which  fixing  a  satisfactory  date  was  difficult. 


BLOOMING  PERIODS  OF  APPLES  115 

The  rule,  sometimes  used,  of  placing  the  date  for  " petals  falling" 
two  days  after  full  bloom  may  operate  fairly  well  in  some  seasons,  but 
in  other  seasons  cannot  be  used;  thus  in  1907,  and  again  in  1908, 
there  were  many  instances  in  which  the  falling  of  petals  was  delayed 
four,  five,  or  more  days  following  full  bloom. 

In  the  fifth  column  is  placed  an  estimate  of  the  amount  of  bloom. 
Various  systems  of  recording  have  been  tried,  including  a  decimal  sys- 
tem with  figures  ranging  from  0  to  1,  but  whatever  is  recorded  is  an 
estimate  and  fine  distinctions  are  of  no  advantage.  The  plan  now  in 
use  recognizes  five  grades ;  namely,  no  bloom,  scant  bloom,  moderate 
bloom,  full  bloom,  and  very  full  bloom,  or  as  being  more  quickly  re- 
corded 0,  1,  2,  3,  and  4.  These  distinctions  serve  every  purpose.  Un- 
usual features  exhibited  by  individuals  have  been  separately  recorded. 

The  ideal  plan  for  recording  flowering  or  any  other  phenomena  of 
plant  life  is  for  one  individual  to  do  the  work  in  each  and  all  years  of 
the  series,  but  this  is  rarely  possible.  Seven  men  share  the  responsi- 
bility of  the  nineteen  years  of  phonological  records  at  this  station ;  for 
the  sixteen  years  to  be  considered  the  field  records  were  made  by  six 
men:  one  made  the  record  for  five  consecutive  years,  one  for  four 
years,  one  for  three  years,  one  for  two  years,  and  two  made  each  the 
record  of  one  year.  An  assistant  has  done  the  work  for  the  last  five 
years,  another  assistant  was  in  charge  for  the  first  two  years ;  for  the 
intervening  years  the  work  was  done  by  senior  or  graduate  students 
under  direction.  Every  effort  was  made  to  secure  as  accurate  a  record 
as  possible.  Beginning  before  any  flowers  were  open,  each  tree  was 
visited  daily  thruout  the  period  of  bloom,  and  during  times  of  high 
temperatures  two  and  in  some  cases  three  visits  were  made  each  day. 

FLOWERING  PERIOD  VARIABLE 

For  central  Illinois  the  flowering  period  for  apples  is  short ;  in 
some  seasons  very  short.  In  some  years  heat  waves  occur  that  bring 
trees  into  full  bloom  with  astonishing  rapidity.  Flowers  thus  sud- 
denly opened  retain  the  ability  to  function  for  a  very  short  time  and 
the  whole  flowering  process  is  over  almost  before  it  is  realized  that 
blooming  time  has  come.  On  the  other  hand  the  spring  season,  in  cer- 
tain years,  has  been  characterized  by  abnormally  low  temperatures,  by 
excessive  rainfall,  or  by  rapidly  alternating  periods  of  heat  and  cold, 
so  that  flowering  of  trees  has  been  very  irregular  and  the  season  much 
prolonged. 

Presumably,  the  heat  waves  occurring  in  this  region  are  more  in- 
tense, and  hence  more  effective  in  pushing  buds  than  in  regions  farther 
north,  and  are  less  intense  and  less  effective  than  in  regions  farther 
south.  However,  comparisons  of  the  length  of  flowering  periods  for 
different  regions  cannot  be  safely  based  upon  latitude  alone,  because 
such  local  features  as  altitude,  slope,  soil,  exposure  to  air  currents,  and 


116  BULLETIN  No.  251  [May, 

proximity  to  bodies  of  water  or  belts  of  timber  may  be  responsible 
for  wide  variations. 

BLOOM  RECORDS  OF  OTHER  LOCALITIES 

Before  entering  upon  detailed  consideration  of  the  bloom  records 
of  this  station,  and  for  convenience  of  comparisons  between  dates  and 
periods  here  and  elsewhere,  brief  mention  may  be  made  of  a  few  of  the 
more  important  records  published. 

Virginia. — In  1905  Price1  of  the  Virginia  Experiment  Station,  gave 
blooming  periods  for  137  varieties  of  apples,  including  thirteen  crab 
varieties.  The  observations  cover  periods  ranging  from  two  to  thirteen 
years,  but  for  about  64  percent  of  the  varieties  the  observations  extend 
over  nine  or  more  years. 

For  each  variety,  the  blooming  period  begins  with  the  opening  of 
the  first  flower  and  ends  two  days  after  full  bloom.  The  earliest  com- 
mencing date  of  bloom  is  April  21,  the  latest  commencing  date,  May  5. 
The  earliest  ending  date  is  April  28,  the  latest,  May  12.  Aside  from 
the  crabs,  which,  with  the  exception  of  Soulard,  are  among  the  earliest 
to  bloom,  there  are  but  eight  of  the  late-blooming  varieties  the  periods 
of  which  do  not,  in  some  degree,  overlap  the  periods  of  varieties  bloom- 
ing earlier.  Considering  all  varieties,  the  flowering  period — from  the 
opening  of  the  first  flower  on  the  earliest  blooming  variety,  to  the  end 
of  the  period  for  the  latest  blooming  variety — extends  from  April  21 
to  May  12,  or  twenty-two  days.  Individual  periods  range  from  five 
days,  as  the  average  of  nine  years  for  Red  June,  to  eleven  days  as  the 
average  of  three  years  for  Seedless ;  3  varieties  have  six-day  periods, 
38  varieties  have  nine-day  periods,  and  5  varieties  have  ten-day 
periods.  The  average  period  for  all  varieties  is  8.14  days. 

The  latitude  of  the  Virginia  Station  is  37°  15' ;  the  elevation 
2,170  feet  above  sea  level.  A  summary  of  meteorological  records  for 
the  twelve-year  period  1893-1904  gives  the  mean  annual  temperature 
as  51.5° ;  mean  maximum,  63.22° ;  mean  minimum,  40.04° ;  the  abso- 
lute maximum,  96° ;  and  the  absolute  minimum,  -13°.  Mean  annual 
precipitation,  39.41  inches. 

New  York. — Flowering  periods  for  a  more  extended  list  of  varie- 
ties, 278  in  number,  were  given  in  March,  1908,  by  Hedrick2  of  the 
Geneva,  New  York,  Station.  Here  the  years  of  observation  ranged 
from  three  to  six,  with  a  little  more  than  one-third  of  the  varieties 
included  under  the  longer  period. 

The  full  flowering  period  extends  from  May  10  to  May  29,  or 
twenty  days;  two  days  less  than  the  corresponding  period  in  Vir- 
ginia, but  the  earliest  flowering  date  in  New  York  precedes  the  ending- 


1  H.  L.  Price,  Va.  Agr.  Exp.  Sta.  Bui.  155. 

"  U.  P.  Hedrick,  N.  Y.  Agr.  Exp.  Sta.  Bui.  299 


1924}  BLOOMING  PERIODS  OF  APPLES  117 

date  of  the  period  for  the  latest  flowering  variety  in  Virginia  by  only 
two  days.  Varietal  periods  range  from  six  days  for  each  of  2  varie- 
ties (Avery  and  Winter  Citron),  and  seven  days  for  11  varieties  to 
twelve  days  for  each  of  5  varieties.  Those  varieties  having  average 
blooming  periods  of  ten  days  or  more  number  121  (or  43.52  percent 
of  the  whole  number).  The  average  period  for  all  varieties  is  9.35 
days. 

In  a  later  publication,  Bulletin  407,  issued  in  May,  1915,  Hedrick 
gives  blooming  records  for  348  varieties  for  the  five-year  period  1910- 
1914.  About  one-half  of  the  varieties  in  this  list  appeared  also  in 
the  earlier  list.  In  this  bulletin,  blooming  periods  for  individual 
varieties  are  not  given,  but  the  varieties  are  classified  to  show  their 
relation  to  each  other  as  to  earliness  or  lateness;  they  summarize  as 
follows : 

Number         Percent 

Very  early 10  2.87 

Early 55  15.81 

Midseason 239  68.68 

Late 34  9.77 

Very  late 10  2.87 

Of  the  blooming  season  Hedrick  says,  ' '  The  blooming  season  of  apples 
at  this  Station  averages  twelve  days.  The  shortest  season  of  bloom 
was  seven  days  in  1913  and  the  longest  season,  eighteen  days  in  1910. 
The  first  date  of  bloom  for  apples  in  1912,  an  average  year,  was  May 
seventh. ' ' 

The  latitude  of  the  New  York  Station,  as  given  in  Bulletin  299, 
is  42°  53' ;  and  the  altitude,  525  feet  above  sea  level.  The  Station  is, 
therefore,  5°  38'  farther  north,  and  has  an  altitude  less  by  1,645  feet 
than  that  of  the  Virginia  Station.  From  these  differences  in  latitude 
and  altitude  considerable  differences  in  flowering  time  of  apples  should 
be  expected.  But  often  there  are  local  conditions  of  soil  or  climate 
that  have  modifying  influences  as  important  as  those  of  latitude  and 
altitude,  and,  from  available  data  it  does  not  seem  possible  to  specify 
the  factors  accountable  for  an  average  full  flowering  period  two  days 
longer  and  an  average  individual  variety  period  1.21  days  shorter 
in  Virginia  than  in  New  York. 

The  mean  annual  temperature  at  the  New  York  Station,  as  given 
in  the  report  for  1917,  ranged  from  43.3°,  in  1885,  to  49.7°  in  3913, 
The  average  for  the  thirty-five  year  period  is  47.4°.  For  the  month 
of  May  the  mean  for  the  thirty-five  years  is  56.5°,  with  the  highest 
mean,  64.09°,  occurring  in  1911,  and  the  lowest  mean,  51.3°,  in  1907. 
Annual  rainfall  has  varied  in  the  thirty-five  years  between  19.35 
inches  in  1899  and  38.69  inches  in  1903 ;  the  average  for  the  period 
is  27.49  inches. 


118  BULLETIN  No.  251  [May, 

Oregon. — Lewis  and  Vincent1  of  the  Oregon  Station  gave  bloom- 
ing records  for  ninety-five  varieties  of  apples  for  the  two  years  1907 
and  1908,  with  diagrams  showing  length  of  time  in  bloom  for  each 
variety.  The  earliest  commencing  date  is  April  5  for  Transcendent 
Crab,  the  latest  commencing  date  April  23  for  Baldwin ;  the  earliest 
date  for  petals  falling  is  April  15  for  Transcendent  Crab ;  the  latest 
for  petals  falling  is  May  2,  and  this  date  applies  to  eight  varieties; 
namely,  Holland  Peppin,  Jonathan,  Missouri  Pippin,  Yellow  New- 
town,  Rome,  Walbridge,  Winesap,  and  York  Imperial. 

The  days  intervening  between  the  earliest  and  latest  beginning 
dates  number  nineteen,  and  between  the  earliest  and  latest  ending 
dates,  eighteen.  The  full  flowering  period  April  5  to  May  2  is  twenty- 
eight  days.  For  individual  varieties,  the  periods  range  from  seven 
days  each  for  Martha  Crab  and  Melon  to  fifteen  days  each  for  Tetofsky 
and  Whitney.  Varieties  having  blooming  periods  ten  or  more  days 
in  length  number  78,  or  82.1  percent  of  the  total  liumber ;  the  mean 
length  of  period  for  all  varieties  is  11.31  days.  Comparing  this  mean 
of  11.31  days  for  all  varieties  for  all  years  with  the  mean  of  7.17  days 
as  found  at  the  Illinois  Station,  it  appears  that  the  average  flowering 
period  in  Oregon  is  longer  by  more  than  50  percent  than  in  Illinois. 
Varieties  in  the  lists  of  the  two  stations  are  for  the  most  part  different, 
there  being  only  fourteen  that  appear  in  both  lists,  but,  whether  com- 
parison is  made  between  these  fourteen  varieties  at  the  two  stations 
or  between  the  entire  lists,  the  difference  in  length  of  period  remains 
the  same.  As  the  Oregon  record  here  considered  covers  but  two  years, 
range  of  variation  of  periods  in  different  years  does  not  appear,  but 
in  Bulletin  82  of  November,  1904,  Lake  refers  to  variation  in  bloom- 
ing as  follows:  "A  very  variable  relation  exists  from  year  to  year 
not  only  between  different  varieties,  but  between  the  various  phases 
of  development  in  the  same  variety,  for  example;  in  1896  Delaware 
Red  and  Domine  were  in  full  bloom  seventeen  days  apart,  but  in  1897 
they  were  in  full  blossom  only  two  days  apart."  Further  regarding 
Fameuse  he  says,  "The  period  from  the  opening  of  first  blossoms  to 
the  time  when  the  tree  is  in  full  blossoms  may  vary  from  year  to  year 
from  three  to  fourteen  days." 

England. — Going  outside  our  own  country,  there  are  available 
certain  English  records  of  apple  blooming  periods  that  may  be  men- 
tioned briefly.  Blooming  periods  for  apples  in  England,  in  general, 
are  longer  than  in  this  country  and  it  does  not  appear  that  they  are 
subject  to  those  extreme  fluctuations  in  duration  of  periods  in  different 
years  that  characterize  records  at  many  points  in  this  country.  Mean 
temperatures  in  England  are  lower  than  at  the  Illinois  Station;  the 


.  I.  Lewis  and  C.  C.  Vincent,  Ore.  Agr.  Exp.  Sta.  Bui.  104. 


1924}  BLOOMING  PERIODS  OF  APPLES  119 

daily  range  is  less,  and  the  hot  waves  that  are  accountable  for  the 
extremely  short  blooming  periods  often  experienced  here  appear  to 
be  wanting. 

Of  English  blooming  periods  Director  F.  J.  Chittenden1  of  the 
Horticultural  Research  Laboratory  at  Wisley  in  Surry  says,  "The 
time  of  flowering  of  apples  varies  between  rather  wide  limits,  both 
as  to  the  commencement  and  as  to  the  period  over  which  the  flowering 
continues.  It  commences  in  southeast  England  about  the  third  week 
in  April  in  early  years  and  continues  into  the  second  week  in  June 
in  late  years.  During  the  four  years  1908-1911,  in  which  records 
have  been  kept  at  Wisley,  our  earliest  apple  to  open,  Red  Astrachan, 
was  in  full  bloom  in  1910  on  April  21 ;  in  1911,  May  2 ;  in  1909, 
May  3  ;  and  in  1908,  May  7 ;  while  the  most  consistently  late-flowering 
variety,  'Royal  Jubilee,'  was  in  full  flower  in  1908  on  May  23;  in 
1909,  May  17;  in  1910,  May  20,  and  in  1911,  May  19."  "The  period 
during  which  one  variety  or  other  of  apple  was  in  full  flower  ( ignoring 
the  few  days,  about  seven  or  eight,  before,  and  the  few,  about  eight 
or  nine,  after  full  flowering  time,  during  which  some  flowers  were 
open)  was,  in  1908,  eighteen  days  (May  6  to  May  23)  ;  in  1909,  twenty 
days  (May  3  to  May  22)  ;  in  1910,  thirty-five  days  (April  21  to 
May  25)  ;  and  in  1911,  eighteen  days  (May  2  to  May  19)." 

The  same  irregularities  that  characterize  blooming  records  in 
Illinois  are  found,  also,  in  the  English  records ;  that  is  to  say,  blooming 
times  and  periods  of  varieties  are  not  constant,  they  do  not  maintain 
a  definite  order  of  blooming,  nor  can  they  be  depended  upon  to  flower 
at  a  time  having  a  definite  relation  to  the  flowering  of  other  varieties. 
The  author  quoted  above  arranges  the  blooming  record  of  168  varieties 
in  order  from  earliest  to  latest,  and  says  of  this  arrangement:  "It 
is  to  be  clearly  understood  that  this  'average  order  of  flowering' 
represents  only  approximately  what  is  likely  to  happen  in  any  par- 
ticular year,  but  it  is  believed  that  it  is  sufficiently  accurate  to  serve 
as  a  guide  as  to  what  varieties  are  most  likely  to  be  in  flower  at  the 
same  time.  One  might  choose  any  of  a  dozen  above  or  below  any 
particular  variety  for  planting  with  it  to  furnish  pollen  with  the 
certainty  that  any  one  of  those  varieties  would  sufficiently  approximate 
its  full-flowering  period  to  the  one  chosen. ' ' 

In  a  paper  read  before  the  Royal  Horticultural  Society2  entitled 
"Observations  on  the  Blossoming  of  Our  Hardy  Cultivated  Fruits," 
Mr.  Cecil  H.  Hooper  gives  a  table  showing  average  blooming  periods 
for  the  years  1908,  1909,  and  1910  of  33  varieties  of  apples  at  Wye, 
Kent,  England.  These  average  periods  range  from  12.66  days  to  22 
days;  the  average  number  of  days  in  flower  is  17.66.  Each  period 


'Jour.  Roy.  Hort.  Soc.  37   (1911-12)   pp.  352-355. 
a  Jour.  Roy.  Hort.  Soc.  36  (1910-1911)  pp.  548-564. 


120  BULLETIN  No.  251  [May, 

begins  with  the  opening  of  the  first  flowers  and  ends  when  nearly  all 
petals  have  fallen.  The  full  period  for  all  varieties  extends  from 
May  1  to  June  9,  or  forty  days.  The  number  of  days  between  open- 
ing of  the  first  flower  and  full  bloom  ranges  for  the  varieties  listed, 
from  four  to  ten,  with  an  average  of  7.42  days,  and  between  full  bloom 
and  completion  of  bloom  from  six  to  sixteen,  with  an  average  of  10.33 
days.  "In  individual  flowers  the  length  of  time  from  opening  to  fall 
of  petals  is  about  seven  days. ' ' 


Detailed  consideration  of  blooming  periods  at  the  Illinois  Sta- 
tion may  now  be  given.  These  records  cover  the  years  1901  to  1916 
inclusive,  and  include  106  varieties.  Of  these  varieties  38  are  recorded 
as  having  bloomed  in  each  of  the  sixteen  years ;  24  varieties  bloomed 
in  each  of  fifteen  years ;  23  in  each  of  fourteen  years ;  11  in  each  of 
thirteen  years ;  5  in  each  of  twelve  years ;  3  in  each  of  eleven  years ; 
and  2  in  each  of  ten  years. 

Six  other  varieties  of  the  older  plantation  have  records  of  bloom 
for  numbers  of  years  less  than  ten,  but  these  are  omitted,  as  are  also 
the  records  for  trees  planted  in  1907  and  1908  and  which  now  have 
records  extending  from  one  to  five  years. 

For  the  sixteen  years,  1901  to  1916,  the  flowering  periods  ranged 
from  ten  days  to  twenty-two  days;  the  average  was  approximately 
sixteen  days.  Eecords  of  two  years,  1906  and  1911,  approximate  the 
average;  seven  years  had  periods  one  to  six  days  longer  than  the 
average,  and  seven  years  had  periods  from  one  to  six  days  shorter 
than  the  average. 

FULL  FLOWERING  PERIODS  FOR  ALL  VARIETIES 

By  the  term  "full  flowering  period"  is  meant  the  period  of  time, 
in  days,  between  the  first  opening  of  a  flower  on  the  earliest  blooming 
variety  and  the  falling  of  petals  from  flowers  of  the  latest  blooming 
variety. 

The  earliest  date  recorded  for  commencement  of  bloom  was  April  2 
in  1910,  the  latest  date  in  the  column  "petals  falling"  was  May  21, 
1904.  The  extremes,  then,  are  fifty  days  apart  and  the  median  date 
would  fall  between  April  26  and  April  27.  But  there  is  here  included 
one  year  so  abnormal  as  to  stand  entirely  apart  from  all  other  years. 
Reference  is  made  to  the  year  1910,  in  which  the  first  flowers  opened 
April  2  and  petals  of  the  latest  flowering  variety  began  falling  April 
19,  one  day  later  than  the  earliest  opening  of  flowers  in  any  other 
year.  If  1910  were  omitted  the  full  flowering  period  for  all  varieties 


1924} 


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122  BULLETIN  No.  251  [May, 

for  fifteen  years  would  extend  from  April  18  to  May  21  or  thirty-four 
days. 

The  accompanying  diagram  shows  graphically  the  length  of  the 
flowering  period  for  each  year  and  the  relation,  as  to  length  of  period, 
of  one  year  with .  another.  Only  in  the  year  1906  did  all  of  the  106 
varieties  bloom.  For  the  other  years  the  numbers  of  varieties  bloom- 
ing ranged  from  76  in  1901,  to  103  in  1904,  1911,  and  1912,  104  in 
1905,  and  105  in  1910.  The  average  number  of  varieties  flowering 
each  year  falls  between  96  and  97. 

EARLY  BLOOMING  VARIETIES 

Dates  of  opening  of  first  flowers  on  earliest  blooming  varieties 
ranged  from  April  2  in  1910  to  May  5  in  1904,  a  difference  of  thirty- 
four  days.  The  average  date  for  the  sixteen  years  was  April  24.  In 
nine  of  the  sixteen  years  this  date  of  first  open  flower  was  later  than 
the  average  and  in  the  other  seven  years  it  was  earlier. 

Numbers  of  varieties  opening  flowers  on  the  first  day  of  bloom,  in 
the  different  years,  vary  between  1  and  46.  The  average  was  between 
8  and  9  (8.68). 

In  1907  Early  Ripe  opened  the  first  flower  April  20  and  was  the 
only  variety  recorded  as  having  open  flowers  on  that  date ;  it  was 
followed  by  7  varieties  on  April  21,  15  on  April  22,  2  on  April  23,  15 
on  April  24,  2  on  April  25,  22  on  April  26,  7  on  April  27,  1  on  April  29, 
2  on  April  30,  4  on  May  1,  and  4  on  May  2,  so  that  for  this  year  the 
varieties,  in  the  opening  of  first  flowers,  were  spread  over  thirteen 
days  and  opened  flowers  on  twelve  of  these  days.  Early  Ripe  is  a 
fairly  consistent  early  bloomer ;  it  appeared  on  the  first  day  of  bloom 
in  eight  of  the  fifteen  years  for  which  it  has  record;  it  appeared 
on  the  second  day  in  1912,  in  which  year  it  was  preceded  by  two 
varieties ;  it  opened  flowers  on  the  third  day  in  each  of  four  years — 
in  1901,  with  17  varieties  one  day  in  advance  of  it;  in  1902,  with  15 
varieties  one  day  in  advance;  in  1903,  with  7  varieties  leading;  and 
in  1906,  with  8  varieties  in  advance.  In  1911,  it  opened  its  first 
flower  on  May  2  in  company  with  17  other  varieties,  while  44 
varieties  were  from  one  to  four  days  in  advance  of  it.  Most  varieties 
exhibited  wider  fluctuations  in  regard  to  relative  position  on  first 
bloom  than  did  Early  Ripe. 

The  only  variety  that  showed  greater  tendency  to  constancy  of 
position  in  relation  to  flowering  of  other  varieties  was  the  Russian 
variety,  Zuzoff,  which  appeared  in  the  lists  of  first  blooming  varieties 
in  eleven  of  its  sixteen  years  of  record.  For  the  other  five  years  this 
variety  appeared  on  the  second  day  of  bloom  in  each  year  and  had 
from  1  to  13  other  varieties  one  day  in  advance  in  opening  blossoms. 

Oldenburg,  which  is  one  of  7  varieties  having  May  1  as  the  earliest 
date  of  open  flowers  in  1901,  one  of  9  having  April  28  as  the  earliest 


1924}  BLOOMING  PERIODS  OF  APPLES  123 

bloom  date  in  1902  and  appearing  in  similar  groups  in  three  other 
years,  was  one  of  22  varieties  to  open  the  fii*st  flowers  on  April  24  in 
1903.  This  was  the  seventh  day  of  bloom  and  35  varieties  were 
recorded  as  having  open  flowers  on  one  or  other  of  the  six  preceding 
days.  In  1905  Oldenburg  did  not  open  flowers  until  the  eighth  day 
of  bloom.  It  was  one  of  15  varieties  opening  the  first  flowers  on  April 
26  while  there  were  5  varieties  with  open  flowers  on  April  19,  and 
65  with  open  flowers  on  dates  between  April  19  and  April  26.  For 
the  year  1905  there  were  104  varieties  blooming  and  of  these  70,  or 
67.3  percent,  had  earlier  dates  of  first  open  flowers  than  did  Olden- 
burg. In  seven  other  years  varying  numbers  of  varieties  had  open 
flowers  earlier  by  one  to  five  days  than  did  Oldenburg. 

Other  varieties  show  the  same  erratic  shifting  of  relative  flowering 
dates  from  year  to  year ;  some  with  more  radical  changes  than  others, 
but  all  showing  that  varietal  flowering  dates  are  in  no  sense  fixed,  but 
vary  within  wide  limits. 

Causes  for  varietal  fluctuations  in  relative  dates  of  first  open 
flowers  must  be  looked  for  in  individual  differences  in  the  vigor  of 
the  trees.  All  trees  are  subjected  to  the  same  wind,  moisture,  and 
temperature  conditions,  and  presumably  the  soil  is  uniform,  but  all 
do  not  behave  in  the  same  manner  with  reference  to  any  of  their 
functions;  one  tree,  in  a  given  year,  makes  greater  growth  than 
another,  has  more  and  better  foliage,  and  exceeds  its  neighbor  in  fruit 
production;  in  another  year  the  performance  of  the  two  may  be 
exactly  reversed  in  all  these  particulars. 

In  the  same  way  response  of  flower  buds  to  the  stimulus  of  advanc- 
ing spring  may  be  quick  and  vigorous  or  tardy  and  weak  depending 
upon  the  condition  of  the  individual. 

LATE  BLOOMING  VARIETIES 

While  some  varieties  have  a  general  tendency  to  bloom  early, 
others  exhibit  the  opposite  tendency,  but  no  variety  in  either  group 
holds  a  particular  position  in  relation  to  other  varieties  with  reference 
to  constancy.  The  period  over  which  the  opening  of  first  flowers 
extends  is  extremely  variable  from  year  to  year  and  its  length  is  gov- 
erned largely  by  temperatures.  A  continued  warm  wave  will  group 
all  varieties  within  a  short  period,  as  was  the  case  in  1915,  when  the 
period  from  the  opening  of  first  flowers  on  the  earliest  blooming 
variety  to  the  opening  of  flowers  on  the  latest  blooming  variety  was 
only  five  days.  Intervention  of  lower  temperatures,  on  the  other 
hand,  will  greatly  extend  the  period.  Thus  in  1905  there  were  seven- 
teen days  between  opening  of  first  flowers  on  earliest  and  latest  varie- 
ties. For  the  other  fourteen  years  this  period  varies  between  eight 
and  fourteen  days,  with  an  average  for  all  years  of  a  fraction  over 
ten  days. 


124  BULLETIN  No.  251  [May, 

The  varieties  that  most  consistently  held  the  position  of  latest 
bloomers  were  Wythe  and  the  Russian  variety,  Repka  Malenka. 
Wythe  occupied  the  position  of  latest  bloomer,  alone  in  1905  and 
1908,  in  company  with  Repka  Malenka  in  1911,  in  company  with 
Repka  Malenka  and  Hall's  No.  3  in  1910,  in  company  with  3  other 
varieties  in  1903  and  1913,  and  with  4  others  in  1906  and  1915.  Thus 
of  the  twelve  years  in  which  Wythe  bloomed  it  had  the  latest  date 
of  first  open  flowers  in  eight  years.  For  the  other  four  years  Wythe, 
in  1902  had  the  same  date  of  first  bloom  as  15  other  varieties ;  it  was 
earlier  by  one  day  than  4  varieties,  and  earlier  by  three  days  than 
Repka  Malenka.  In  1904  Wythe  stood  alone  with  first  bloom  on  May 
11,  but  was  two  days  earlier  than  Sandy  Glass.  In  1912  Wythe  had 
first  bloom  on  May  3,  in  company  with  8  other  varieties,  and  was  one 
day  in  advance  of  Repka  Malenka,  Garfield,  and  Hall's  No.  3.  For 
1916  Wythe  had  the  same  date  of  first  bloom  as  11  other  varieties, 
bloomed  one  day  earlier  than  13  other  varieties  and  two  days  earlier 
than  Repka  Malenka. 

Repka  Malenka  had  the  latest  date  of  first  open  flower  in  ten  of 
the  fourteen  years  in  which  it  flowered ;  it  occupied  this  position 
alone  in  1902  and  1916,  and  was  accompanied  by  Wythe  or  from 
1  to  4  other  varieties  in  the  other  eight  years.  In  1905  Repka  Malenka 
was  four  days,  and  in  1908  two  days  earlier  than  Wythe ;  in  1904 
it  was  four  days  earlier,  and  in  1914  three  days  earlier  than  the  latest 
flowering  varieties. 

Other  varieties  that  have  had  place  among  latest  bloomers  are 
Hall's  No.  3  in  1906,  1909,  1910,  1912,  1913,  and  1915;  Rome  in 
1906,  1909,  1913,  and  1915  ;  Grimes  in  1903  ;  Willow  in  1913  ;  Hunts- 
man in  1914 ;  Tolman  in  1903 ;  and  about  a  dozen  other  little-known 
varieties,  mostly  Russian. 

As  before  stated,  no  variety  has  proved  constant  in  its  flowering 
position  as  related  to  other  varieties,  but  perhaps  there  is  less  shifting 
of  dates  and  positions  among  the  late  flowering  than  among  the  very 
early  flowering  varieties. 

BLOOMING  PERIOD  OF  1910 

For  the  year  1910  the  seasonal  abnormality  of  bloom  was  so  great 
that  attending  circumstances  deserve  mention  in  some  detail.  As 
stated,  the  first  open  flowers  appeared  April  2  and  petals  were  fall- 
ing from  the  latest  blooming  variety  on  April  19,  a  period  of  eighteen 
days.  A  period  of  the  same  length  was  recorded  for  1909,  one  a  day 
shorter  in  1904,  and  another  a  day  longer  in  1905.  Nine  of  the  re- 
maining twelve  years  had  periods  from  two  to  eight  days  shorter  and 
for  three  years  the  periods  were  three  and  four  days  longer. 

The  varieties  commencing  bloom  on  April  2  were  Early  Ripe  and 
Zuzoff;  these  were  followed  April  3  by  open  flowers  on  9  varieties; 

.in 


1924]  BLOOMING  PERIODS  OF  APPLES  125 

namely,  Borovinka,  Borsdorf,  Hargrove,  Isham,"0simoe,  Ostrakoff, 
Red  Anis,  Red  Stripe,  and  Yellow  Siberian  Crab.  First  bloom 
appeared  on  11  varieties  April  4,  on  20  varieties  April  5,  on  8  varieties 
April  6,  on  16  varieties  April  7,  on  12  varieties  April  8,  on  19  varieties 
April  9,  on  Garfield,  Grandmother,  Ox  Sweet,  Roe's  Tolman,  and 
Rome  on  April  11,  and  on  Hall's  No.  3,  Repka  Malenka,  and  Wythe 
on  April  12. 

The  varieties  flowering  number  105  covering  the  full  list  with  the 
exception  of  Bogdanoff.  Of  the  two  varieties  opening  flowers  April  2, 
Zuzoff  completed  its  period,  that  is  the  petals  were  falling,  on  April  9, 
and  April  10  is  the  date  recorded  for  falling  petals  of  Early  Ripe. 
The  last  variety  to  reach  the  stage  of  falling  petals  was  Repka  Malenka 
on  April  19,  and  of  the  two  varieties  having  the  same  beginning  date, 
April  12,  Wythe  reached  the  end  of  its  flowering  period  April  17, 
and  Hall's  No.  3  on  April  18. 

Individual  periods  for  the  105  varieties  that  bloomed  ranged  in 
length  from  four  to  nine  days,  divided  as  follows: 

Periods  of 

— four  days 7  varieties 

— five  days 11  varieties 

— six  days 29  varieties 

— seven  days 23  varieties 

— eight  days      22  varieties 

— nine  days 13  varieties 

These  individual  flowering  periods  were  not  affected  by  the 
abnormal  earliness  of  bloom ;  they  ranged  much  the  same  as  in  normal 
years.  It  appears  that  the  whole  flowering  period  was  simply  moved 
forward  until  the  end  of  bloom,  for  the  latest  flowering  variety  and 
the  earliest  opening  of  flowers  in  any  other  year  overlap  by  only 
one  day. 

The  earliness  of  bloom  is  directly  attributable  to  the  abnormal 
meteorological  conditions  that  prevailed  during  March.  This  month 
was  dry ;  rain  fell  on  only  four  days,  the  18th,  19th,  26th,  and  30th, 
with  an  aggregate  precipitation  of  only  .38  inch.  The  first  two  days 
of  the  month  were  recorded  as  cloudy ;  of  the  days  following,  eighteen 
were  partly  cloudy  and  eleven  clear.  The  mean  daily  temperature 
for  the  month  was  52.3°,  12°  above  normal;  the  mean  minimum, 
37.7° ;  and  the  mean  maximum,  63°.  The  last  frost  of  the  month 
occurred  on  the  morning  of  March  21,  and  there  were  early  morning 
frosts  on  thirteen  of  the  preceding  days. 

For  the  last  fifteen  days  of  the  month  the  mean  temperature  was 
58.4° ;  the  mean  maximum,  73.9° ;  and  the  mean  minimum,  44.7°. 
The  absolute  maximum  was  85°  on  March  24.  There  were  four  days 


126  BULLETIN  No.  251  [May, 

on  which  the  maximum  was  above  80°  and  ten  days  on  which  it  was 
above  70°. 

For  the  eighteen-day  period  of  bloom,  April  2  to  19,  rain  ag- 
gregating .82  inch  fell  on  eight'  days ;  the  last  three  days  were  cloudy, 
eleven  days  were  partly  cloudy,  and  four  days  were  clear.  The  mean 
daily  temperature  was  53.4° ;  the  mean  maximum,  65.6° ;  and  the 
mean  minimum,  42.1°. 

The  mean  daily  temperature  for  the  flowering  period  was  from 
1.4°  to  5.3°  lower  in  three  years,  namely  1904,  1907,  and  1908,  and 
from  2.2°  to  13.7°  higher  in  the  twelve  other  years. 

COMPARISON  OF  THE  PERIODS  FOR  THE  YEARS  1904  AND  1910 

Having  given  the  temperatures  for  the  month  preceding  and  for 
the  period  of  bloom  of  the  year  1910  in  which  blooming  was  abnormally 
early,  it  will  be  of  interest  to  make  comparison  with  the  blooming 
period  for  1904,  in  which  year  the  blooming  period  was  the  latest  of 
those  recorded.  In  1904  there  were  103  varieties  blooming,  two  less 
than  in  1910.  ' 

Three  varieties  flowered  in  1910  that  did  not  flower  in  1904,  and 
one  variety  flowered  in  1904  that  did  not  flower  in  1910.  Eliminating 
these  four  varieties  limits  the  comparison  of  the  two  years  to  102 
varieties  that  have  records  for  both  years.  The  full  flowering  periods 
for  the  two  years  differ  by  but  one  day ;  seventeen  days  in  1904,  and 
eighteen  days  in  1910,  but  the  beginning  date  in  1910  was  thirty-four 
days  in  advance  of  the  beginning  date  in  1904.  The  two  dates  were 
April  2  in  1910  and  May  5  in  1904.  As  the  periods  differ  in  length 
by  one  day  the  ending  dates,  April  19  in  1910  and  May  21  in  1904, 
are  separated  by  thirty-three  days. 

Flowering  periods  for  individual  varieties  tended  to  concentration 
about  the  six-,  seven-,  and  eight-day  periods  in  both  years;  in  1904, 
77  or  75.49  percent  of  the  varieties  fell  under  these  three  periods  and  in 
1910,  71  or  69.60  percent  of  the  varieties  were  recorded  as  in  these 
periods. 

The  day-groups  in  1904  numbered  eight,  with  a  range  of  four  to 
fourteen  days ;  in  1910  there  were  six  day-groups  with  a  range  of  four 
to  nine  days.  In  1904  there  were  two  varieties  having  ten-day  periods 
and  one  with  a  fourteen-day  period.  Distribution  of  varieties  into 
periods  differing  in  length  by  one  day  was  as  follows: 


1924]  BLOOMING  PERIODS  OF  APPLES  127 

Varieties  having  each  a  period  of 

1904  1910 

— four  days 3  7 

— five  days 6  11 

— six  days 16  27 

— seven  days 28  22 

— eight  days 33  22 

— nine  days 13  13 

— ten  days 2  0 

— eleven  days 0  0 

— twelve  days 0  0 

— thirteen  days 0  0 

— fourteen  days 1  0 


102  102 

The  average  period  was  7.34  days  for  1904  and  6.78  days  for  1910 ; 
longer  by  .56  day  in  the  year  when  the  blooming  period  occurred 
thirty-four  calendar  days  later  than  in  the  year  of  early  bloom.  It 
would  be  reasonable  to  expect  that  in  contrasting  the  blooming  periods 
of  two  years,  one  of  which  was  more  than  a  month  later  in  the  season 
than  the  other,  the  periods  of  individual  varieties  would  be  shorter 
and  concentrated  under  fewer  day-periods  in  that  year  in  which  the 
blooming  time  was  latest  in  season.  This  is  expected  because  the  more 
powerful  action  of  the  sun  and  the  presumed  greater  aggregate  of 
heat  units  in  the  advanced  season  should  so  stimulate  plant  functions 
that  blooming  of  varieties  would  proceed  rapidly  and  result  in  con- 
centration within  narrow  time  limits  of  short  individual  periods.  In 
this  case,  however,  the  reverse  was  true.  Not  only  were  the  full  flower- 
ing periods,  altho  separated  by  more  than  a  month,  of  nearly  equal 
length,  but  individual  periods  had  a  shorter  average  length  in  the  early 
year  and  there  were  twice  as  many  varieties  having  four-  and  five-day 
periods  as  in  the  later  year. 

Temperatures  preceding  and  during  the  blooming  period  of  1904 
may  now  be  examined,  considering  first  a  period  of  thirty-two  days 
from  April  3  to  May  4,  which  equals  the  period  March  1  to  April  2 
considered  in  relation  to  the  bloom  in  1910.  For  this  period  the  maxi- 
mum temperature  was  80° ;  minimum,  22° ;  and  mean,  46.60°.  Dif- 
ferences between  the  temperatures  for  the  two  years  are  most  readily 
compared  by  placing  them  in  parallel  columns  as  below. 

1904                              Maximum  Minimum            Mean 

April    3-May    4 .Absolute  80°  Absolute  22°         46.60° 

Mean  57.97°  Mean   35.84° 
1910 

March  1-April  1 Absolute  85°  Absolute  17°         52.30° 

Mean        63°  Mean     37.7° 

The  absolute  maximum  for  the  early  period  of  1910  was  5°  higher 
than  for  the  later  period  of  1904  and  this  difference  holds  approxi- 
mately for  the  mean  maxima  of  the  two  periods. 

The  absolute  minimum  for  1910  was  5°  lower  than  for  1904,  but 
the  average  of  minimum  temperatures  for  the  periods  under  consid- 


128  BULLETIN  No.  251  [May, 

eration  (for  the  two  years)  was  nearly  2°  higher  for  1910  than  for 
1904.  Mean  temperatures  for  the  periods  were  46.60°  for  1904,  and 
52.30°  for  1910 ;  the  mean  for  the  year  of  early  bloom  5.7°  higher  than 
for  the  year  of  late  bloom. 

Comparing  actual  blooming  periods — April  2  to  19  in  1910,  and 
May  5  to  21  in  1904 — it  is  found  that  higher  temperatures  prevailed 
in  1904  than  in  1910.  The  maximum  in  1904  was  84°,  in  1910,  80°, 
with  an  average  maximum  in  1904  of  70.05°  and  in  1910  of  65.6° ;  the 
1904  average  was  4.45°  higher  than  in  1910.  Minimum  temperatures 
were  41°  for  1904  and  30°  for  1910;  the  average  minimum,  48°  for 
1904  and  42.1°  in  1910;  the  1904  average  was  nearly  6°  higher  than 
the  average  of  1910.  Mean  daily  temperatures  were  58.91°  for  1904 
and  53.4°  for  1910;  that  for  the  year  of  late  bloom  was  5.51°  higher 
than  that  for  the  year  of  early  bloom. 

For  the  thirty-two  days  preceding  bloom  in  1904,  temperatures  of 
32°  or  lower  were  recorded  on  twelve  days ;  for  the  similar  period  in 
1910,  on  ten  days.  During  the  blooming  period  in  1904  there  were 
no  frosts,  but  in  1910  frosts  occurred  on  five  days. 

From  this  examination  of  temperatures,  it  appears  that  the  heat 
stimulus  for  the  period  of  thirty-two  days  preceding  the  first  opening 
of  flowers  was  somewhat  greater  from  March  1  to  April  1  in  1910  than 
it  was  from  April  3  to  May  4  in  1904,  and  that  for  the  periods  of 
bloom  there  were  higher  temperatures  for  the  May  period  of  1904 
than  for  the  April  period  of  1910. 

The  chief  reason  for  the  unseasonable  advance  of  flower  buds  in 
1910  appears  to  rest  in  the  high  temperatures  that  prevailed  during 
the  period  of  thirty-two  days  just  preceding  £he  opening  of  flowers. 
The  temperatures  thruout  the  period  of  blooming  continued  suffi- 
ciently high  to  concentrate  varietal  periods  into  six  groups  of  four  to 
nine  days,  with  a  shorter  average  individual  period  than  is  recorded 
for  1904,  when  the  bloom  came  a  full  month  later  in  the  season. 

To  what  extent  differences  in  moisture  supplemented  the  tempera- 
ture differences  between  the  two  seasons  compared  is  not  known,  but  it 
seems  probable  from  differences  in  precipitation  that  the  influence 
may  have  been  important.  For  the  thirty-two-day  periods  preceding 
bloom  in  the  two  years  the  rainfall  and  cloudiness  are  recorded  as 

follows : 

Bainfall  No.  of  days  on  Clear  Partly  cloudy  Cloudy 

(inches')  which  rain  fell  days                days  days 

1904 3.44                    7  10                    18  4 

1910 38                    4  12                     18  2 

Rainfall  for  the  1904  period  was  nine  times  that  of  the  1910  period. 
Clear  days  were  two  less  and  cloudy  days  two  more  than  in  1910.  The 
heaviest  rainfall  of  1910  was  less  than  the  least  fall  in  1904  and  the 
heaviest  single  rain  (1.61  inches)  in  1904  was  more  than  four  times  the 
total  for  the  period  in  1910. 


BLOOMING  PEFJODS  OF  APPLES  129 

For  the  seventeen-day  duration  of  bloom  in  1904,  the  rainfall  was 
.94  inch,  distributed  over  nine  days,  two  of  which  record  only  a  trace. 
In  1910  the  rainfall  for  the  eighteen-day  period  of  bloom  was  .82  inch, 
distributed  over  ten  days,  and  again  two  of  the  days  record  a  trace 
only.  Five  of  the  seventeen  days  in  1904  and  four  of  the  eighteen  days 
in  1910  were  clear.  Eleven  days  of  the  periods  in  each  of  the  two  years 
were  partly  cloudy;  one  in  1904  and  three  in  1910  were  entirely 
cloudy. 

After  blooming  began,  varieties  responded  much  more  rapidly  in 
1904  than  they  did  in  1910.  This  is  shown  by  the  fact  that  only  two 
varieties  opened  flowers  on  the  earliest  date  of  bloom  in  1910  and  at 
the  end  of  the  fifth  day  from  the  beginning  of  bloom  only  50,  or  47.6 
percent  of  all  varieties  had  open  flowers ;  whereas  in  1904  there  were 
thirteen  varieties  that  opened  flowers  on  the  first  day  of  bloom  and  at 
the  end  of  the  fifth  day  99,  or  96.11  percent  were  recorded  as  having 
open  flowers. 

Comparing  flowering  periods  for  individual  varieties,  it  appears 
that  23  varieties  had  periods  of  equal  length  in  the  two  years,  while 
for  79  varieties  the  periods  were  either  longer  or  shorter  in  one  year 
than  in  the  other.  Thus  19  varieties  had  periods  one  day  longer  in 
1904  than  in  1910,  and  13  varieties  had  periods  one  day  longer  in  1910 
than  in  1904.  There  were  13  varieties  with  periods  two  days  longer 
in  1904  than  in  1910,  and  12  varieties  with  periods  two  days  longer  in 
1910  than  in  1904 ;  13  varieties  whose  periods  were  three  days  longer 
in  1904  than  in  1910,  and  3  whose  periods  were  three  days  longer  in 
1910  than  in  1904 ;  3  varieties  with  periods  four  days  longer  in  1904 
than  in  1910,  and  only  one  with  a  period  four  days  longer  in  1910  than 
in  1904.  Two  other  varieties  exhibited  still  wider  differences.  Grand- 
mother, which  had  a  five-day  period  in  1910,  had  a  ten-day  period  in 
1904,  a  difference  of  five  days,  or  a  period  twice  as  long  in  the  year 
of  late  bloom  as  in  the  year  of  early  bloom.  The  extreme  of  difference 
is  seen  in  periods  of  Repka  Malenka,  which  has  a  record  of  eight  days 
in  1910  and  of  fourteen  days  in  1904,  a  period  six  days  longer  in  the 
year  of  late  bloom  than  in  the  year  of  abnormally  early  bloom. 

Fluctuations  in  length  of  flowering  periods  from  year  to  year  are 
the  rule  rather  than  the  exception  and  further  illustrations  will  be 
given  elsewhere.  But  the  differences  between  periods  in  these  two 
years,  and  the  fact  that  for  50  varieties  the  periods  were  from  one  to 
six  days  longer  in  1904  than  in  1910,  and  that  29  other  varieties  had 
periods  from  one  to  four  days  longer  in  1910  than  in  1904,  suggests 
the  operation  of  influences  aside  from  temperature  and  moisture  and 
about  which  nothing  definite  is  known. 


130  BULLETIN  No.  251  [May, 

VARIETAL  FLOWERING  PERIODS 

For  the  different  years  the  average  varietal  flowering  period  for 
all  varieties  blooming  in  the  particular  year,  ranged  from  five  to  ten 
days.  This  average  was  five  days  in  1901  and  1915,  six  days  in  1908 
and  1912,  seven  days  in  each  of  six  years,  eight  days  in  each  of  three 
years,  nine  days  in  1903  and  1914,  and  ten  days  in  1907. 

The  extremes  in  length  of  blooming  periods  for  individual  varieties 
may  be  near  together  in  one  year  and  widely  separated  in  another 
year ;  there  is  great  variation  in  this.  Thus  in  1907,  a  year  in  which 
only  82  varieties  bloomed,  the  minimum  period  of  three  days  was  rep- 
resented by  2  varieties,  the  maximum  period  of  seventeen  days  by  1 
variety,  and  each  number  of  days  falling  between  three  and  seventeen 
was  represented  by  1  to  13  varieties ;  this  largest  number,  13,  falling 
to  the  twelve-day  period.  The  total  number  of  periods,  each  differing 
from  its  neighbor  by  one  day,  was  fifteen.  At  the  other  extreme,  the 
year  1915  had  the  record  of  a  concentration  of  100  varieties  into  three 
blooming  periods ;  7  varieties  had  each  a  four-day  period,  57  varieties 
had  five-day  periods,  and  36  varieties  had  six-day  periods.  Next  to 
1915  in  number  of  periods  differing  by  one  day,  is  the  year  1902  with 
four  periods  ranging  from  five  to  eight  days  in  length.  The  87 
varieties  were  distributed  as  follows:  with  five-day  periods,  5 
varieties ;  with  six-day  periods,  34  varieties ;  with  seven-day  periods, 
31  varieties,  and  with  eight-day  periods,  17  varieties.  Each  of  the 
years  1901  and  1912  concentrates  the  flowering  record  into  five  groups 
ranging  from  four  to  eight  days.  Other  years  range  thru  six,  seven, 
eight,  nine,  ten,  and  eleven  groups  each,  and  then  follow  the  maximum 
of  fifteen  groups  in  1907,  as  already  mentioned. 

Concentration  into  few  groups,  or  distribution  into  many  groups, 
follows  the  full  length  of  flowering  period ;  that  is,  from  the  opening 
of  the  first  flower  on  the  earliest  blooming  variety  to  the  fall  of  the 
petals  on  the  latest  blooming  variety,  with  a  regularity  which,  altho 
not  perfect,  approximates  the  expectation.  The  shortest  blooming 
period  was  ten  days  in  1915,  and  in  that  year  appeared  the  maximum 
of  concentration :  three  groups  of  four,  five,  and  six  days,  respectively. 
The  longest  blooming  period  of  twenty-two  days  was  recorded  for  the 
year  1907,  in  which  year  occurred  the  maximum  distribution  into 
fifteen  groups  with  periods  three  to  seventeen  days  in  length. 

Next  below  the  maximum  in  length  of  flowering  period  come  the 
two  years  1903  and  1908  each  with  a  period  of  twenty-one  days.  In 
the  earlier  year  the  99  varieties  flowering  fall  into  ten  groups  with 
varietal  periods  ranging  from  five  to  fourteen  days;  in  1908  the  97 
varieties  fall  into  eleven  groups  with  varietal  periods  ranging  from 
three  to  sixteen  days,  but  with  no  representatives  for  the  nine-,  eleven-, 


1924] 


BLOOMING  PERIODS  OF  APPLES 


131 


and  fourteen-day  groups ;  90  of  the  varieties  were  in  the  five  groups 
with  three  to  seven-day  periods;  the  remaining  seven  were  scattered 
in  six  groups  of  greater  length. 

The  full  flowering  period  in  1905  was  nineteen  days,  that  of  1909, 
eighteen  days ;  in  both  years  the  number  of  groups  was  eleven,  but  in 
1909  the  longest  period  was  one  day  longer  than  the  longest  period  in 
1905. 

Distribution  of  varieties  into  groups  according  to  length  of  bloom- 
ing period  is  shown  for  each  year  in  the  accompanying  table,  together 
with  the  number  of  varieties  blooming  and  the  average  varietal  period 
for  each  year. 

TABLE  2. — DISTRIBUTION  OF  VARIETAL  BLOOMING  PERIODS  IN  EACH  YEAR 


Year 

Number 
of 
varieties 
blooming 

Length  of  blooming  period  in  days 

Average 
varietal 
period, 
diiys 

3 

4 

5 

6 

7 

8 

9 

10  |  11 

12 

13 

14 

15 

16 

17 

1901 
1902 
1903 
1904 
1905 
1906 
1907 
1908 
1909 
1910 
1911 
1912 
1913 
1914 
1915 
1916 

76 
87 
99 
103 
104 
106 
82 
97 
100 
105 
103 
103 
102 
84 
100 
94 

39 

19 
5 
7 
6 
5 
6 
1 
34 
20 
11 
11 
42 
15 
4 
57 
23 

11 
34 
10 
17 
10 
32 
8 
32 
21 
29 
18 
32 
25 
6 
36 
8 

6 
31 

5 
28 
11 
39 
5 
9 
12 
23 
12 
11 
12 
1 

1 
17 
26 
33 
25 
17 
10 
1 
25 
22 
34 
9 
11 
9 

4.83 
6.69 
9.20 
7.30 
8.23 
7.00 
9.93 
5.89 
7.02 
6.77 
7.35 
5.70 
7.58 
9.03 
5.29 
7.02 

4 
13 
21 
10 
6 

ii 

13 
17 

12 
2 
21 
1 
12 
1 
3 

13 

16 

2 

4 
1 

"3 

3 
1 

3 
1 
11 

"2 

3 

1 

2 
2 
1 

1 
13 

3 
7 
4 
9 
1 

13 

1 
1 

4 
1 

4 

i 

3 
2 

1 
1 

1 

7 

12 

29 

21 
27 

5 
4 

3 

1 

7 
4 

16 

19 

23 

1 

AMOUNT  OF  BLOOM 

While  record  of  the  amount  of  bloom  has  been  kept  under  the  five 
gradations — none,  scant,  moderate,  full,  and  very  full — as  elsewhere 
explained,  it  is  necessary  to  consider,  from  a  practical  standpoint,  only 
three  divisions ;  namely,  no  bloom,  amount  too  small  to  suggest  a  crop 
of  fruit,  and  sufficient  to  promise  a  crop.  The  amount  of  bloom  is  not 
open  to  exact  determination  and  the  record,  at  best,  is  only  an  estimate ; 
but  effort  ha«  been  made  to  keep  the  basis  of  estimate  as  uniform  as 
possible.  It  is  believed  that  the  record  will  be  helpful  in  the  summa- 
tion of  the  characteristics  of  varieties,  in  segregating  those  with  well- 
defined  tendencies  towards  insufficient  bloom  from  those  having  the 
opposite  tendency,  and  in  advancing  studies  that  may  be  undertaken 
into  the  causes  for  blooming  tendencies  exhibited. 

Observation  of  the  blooming  of  apple  trees  year  after  year  conveys 
a  very  definite  impression  of  wide  seasonal  differences  in  behavior  of 


132  BULLETIN  No.  251  [May, 

varieties  and  individuals,  of  very  unequal  response  to  exterior  condi- 
tions observed  and  assumed  to  exert  influence  either  as  stimuli  to  in- 
creased activity  or  as  agents  operating  to  retard  or  diminish  plant 
processes,  and  of  the  fact  that  factors  governing  performance  are 
complex  and  dependent  upon  physiological  changes  that  are  difficult 
to  understand  or  interpret  rightly. 

Amount  of  bloom  is  not  determined  at  blooming  time,  as  the  buds 
are  formed  the  preceding  summer;  they  make  small  advance  in  the 
fall  and  may  even  make  slight  growth  during  the  winter.  They  push 
and  make  rapid  or  slow  development  in  the  spring,  according  to  the 
climatic  conditions  of  the  season,  but  whether  the  amount  is  large  or 
small  in  a  large  measure  must  be  controlled  by  conditions  and  sur- 
roundings of  the  trees  during  the  formative  period,  nine  or  ten  months 
preceding  the  opening  of  flowers  in  spring. 

Classified  into  the  three  divisions — no  bloom,  not  enough  for  a 
crop,  and  sufficient  for  a  crop  of  fruit — the  1,696  records  for  the  106 
varieties  for  sixteen  years  divide  as  follows :  no  bloom,  151 ;  not 
enough  to  make  a  crop,  485 ;  and  enough  to  promise  a  crop,  1,060. 
Deficiency  records  constitute  371/2  percent  of  the  total,  leaving  62!/o 
percent  to  represent  cases  of  sufficiency  or  excess  of  bloom. 

The  151  records  of  failure  to  bloom  are  distributed  in  numbers 
ranging  from  1  to  30  thruout  fifteen  years ;  only  in  the  year  1906  did 
all  varieties  produce  flowers.  The  larger  number  of  failures,  30, 
occurred  in  1901 ;  in  1907  the  number  was  24;  in  1914,  22;  in  1916, 
12;  with  numbers  less  than  10  in  the  other  years. 

Records  of  scant  or  insufficient  bloom  are  much  more  numerous 
than  those  of  no  bloom,  constituting,  as  they  do,  28.6  percent  of  all 
records.  Numbers  of  varieties  appearing  in  this  class,  in  the  different 
years,  range  from  1  to  59  and  are  as  irregular  in  distribution  as  are 
numbers  in  the  class  having  no  bloom. 

In  thirteen  of  the  sixteen  years,  numbers  of  varieties  in  the  scant 
bloom  column  are  larger  than  in  the  no  bloom  column,  but  it  does  not 
follow  that  high  numbers  in  the  scant  bloom  column  are  always  ac- 
companied by  low  numbers  in  the  no  bloom  column ;  thus  in  1901  with 
the  maximum  of  30  in  the  no  bloom  column  there  are  33  in  the  scant 
Moom  column,  and  in  1907  the  respective  numbers  are  24  and  41.  On 
the  other  hand,  the  two  highest  numbers  of  varieties  in  the  scant  bloom 
column  are  associated  with  low  numbers  in  the  no  bloom  column,  as 
59  scant  bloom  and  3  no  bloom  in  1911 ;  51  scant  bloom  and  2  no 
bloom  in  1905.  For  the  three  years  1913-1915,  the  reverse  is  true; 

1913  has  1  in  the  scant  bloom  column  to  4  in  the  no  bloom  column ;  for 

1914  the  numbers  are  14  and  22,  and  for  1915,  3  and  6  respectively. 
The  most  satisfactory  index  of  performance  as  to  amount  of  bloom 

is  found  in  the  distribution  of  varieties  between  the  two  groups,  in- 
sufficient or  no  bloom,  and  bloom  sufficient  for  a  crop. 


1924}  BLOOMING  PERIODS  OF  APPLES  133 

Examining  the  record,  it  appears  that  1913  was  the  year  of  maxi- 
mum performance,  for  101,  or  95.28  percent,  of  the  106  varieties  car- 
ried sufficient  bloom.  Next  to  this  is  1915  with  97,  or  91.51  percent, 
of  the  varieties  having  satisfactory  production.  At  the  other  extreme 
are  the  years  1902  and  1907,  each  having  only  41,  or  38.68  percent,  of 
the  varieties  in  the  group  having  sufficient  bloom.  The  twelve  other 
years  have  numbers  of  varieties  in  this  same  group  ranging  from  43  to 
91,  with  percentages  from  40.57  to  85.85. 

It  is,  perhaps,  worthy  of  note  that  only  ninety-two  records  appear 
of  varieties  having  exceptionally  heavy  bloom;  these  are  distributed 
by  years  as  follows :  30  varieties  in  1914,  22  in  1915,  15  in  1902,  11  in 
1904,  4  in  each  of  the  years  1901  and  1916,  and  3  in  each  of  the  years 
1903  and  1912.  For  the  seven  consecutive  years  1905  to  1911,  and  for 
the  year  1913 — eight  years  in  all — there  are  no  varieties  represented  in 
the  enumeration  of  cases  of  very  heavy  bloom.  The  varieties  that  do 
have  place  among  those  having  very  full  bloom  in  one  or  more  years 
number  58 ;  of  these  32  appear  in  the  list  but  once,  21  appear  twice, 
3  appear  three  times,  1  four,  and  another  five  times.  There  are  three 
cases  in  which  the  years  of  extra  heavy  bloom  were  consecutive  and  all 
for  the  years  1914  and  1915;  the  varieties  are  Pointed  Pipka,  Red 
Aport  and  Borsdorfer,  the  latter,  eleven  years  before  was  credited  with 
a  third  year  of  heavy  bloom.  There  are  also  twelve  cases  involving  9 
varieties  in  which  years  of  very  heavy  bloom  were  separated  by  only 
one  year,  and  that  year  had  full  bloom  in  one  case,  moderate  bloom  in 
seven  cases,  scant  bloom  in  three  cases,  and  none  in  one  case. 

The  relation  of  very  heavy  bloom  to  bloom  in  preceding  and 
following  years  has  been  examined  and  from  the  results  it  may  be 
stated  that  in  four  cases  where  heavy  bloom  occurred  in  the  first  year 
of  record,  the  performance  of  the  preceding  year  was  unknown;  of 
the  eighty-eight  remaining  records  of  the  next  preceding  years,  sixty- 
two,  or  70.45  percent,  had  either  full  or  moderate  bloom  (enough  to 
promise  a  crop),  while  twenty-six,  or  29.55  percent,  recorded  scant 
bloom  or  none.  Following  heavy  bloom  there  were  four  years  in  which 
heavy  bloom  occurred  in  the  last  year  of  record  with  no  record  for  the 
following  year.  The  eighty-eight  records  of  following  years  divide  as 
follows:  sufficient  bloom  for  a  crop  in  fifty-seven,  or  64.77  percent, 
and  insufficient  or  no  bloom  in  thirty-one,  or  35.23  percent. 

For  the  twenty-one  varieties,  each  appearing  twice  in  the  list  of 
those  recording  heavy  bloom,  there  are  two  cases  in  which  the  years  of 
heavy  bloom  were  consecutive,  five  cases  in  which  there  was  alterna- 
tion, with  sufficient  bloom  in  the  intervening  year,  and  fourteen  cases 
in  which  the  years  of  very  heavy  bloom  were  separated  by  eight  to 
twelve  years. 


134  BULLETIN  No.  251  [May, 

The  three  varieties  each  recorded  as  having  heavy  bloom  in  three 
years  were  Borsdorfer,  Hibernal,  and  Willow.  Borsdorfer  had  the 
highest  record  of  any  variety,  for  in  not  one  of  the  sixteen  years  was 
there  a  deficiency  in  bloom ;  the  record  of  this  variety  began  with  full 
bloom  in  1901,  extra  heavy  bloom  in  1902  followed  by  three  years  of 
full  bloom,  a  year  of  moderate  bloom,  then  full  bloom,  again  followed 
by  a  year  of  moderate  bloom,  then  five  consecutive  years  of  full  bloom 
followed  by  very  heavy  bloom  in  1914  and  1915,  ending  with  full  bloom 
in  1916.  Hibernal,  while  having  very  full  bloom  in  1902,  1904,  and 
1915,  and  sufficient  for  a  crop  in  four  other  years,  had  no  bloom  in 
1901,  1907,  and  1914,  and  bloom  insufficient  for  a  crop  in  1903,  1905, 
1912,  and  1916.  A  summary  for  this  variety  shows  nine  years  of 
sufficient  bloom  and  seven  years  of  deficient  bloom. 

Willow  began  with  very  full  bloom  in  1901  and  duplicated  the  per- 
formance in  1903,  with  a  year  between  of  scant  bloom;  it  had  full 
bloom  in  1904  and  of  the  following  ten  years,  six  had  each  enough  for  a 
crop  and  four  less  than  enough,  then  came  a  year  df  very  full  bloom  in 
1915  followed  by  a  deficiency  in  1916 ;  or,  for  the  sixteen  years,  ten 
had  enough  bloom  and  six  had  deficiencies  altho  in  no  year  was  there 
entire  absence  of  bloom. 

The  variety  recorded  as  having  very  full  bloom  in  four  years  was 
Oldenburg;  the  years  of  very  full  bloom  were  1902,  1904,  1914,  and 
1916 ;  between  each  of  these  pairs  was  a  year  of  moderate  bloom.  The 
record  began  with  scant  bloom  in  1901,  then  for  the  years  1905  to 
1913  inclusive  were  six  years  of  bloom  sufficient  for  a  crop,  two  years 
with  insufficient  bloom,  and  one  year  with  no  bloom — a  record  for  the 
sixteen  years  of  twelve  years  in  which  the  bloom  was  good  and  four 
in  which  it  was  poor. 

Borovinka  reached  the  maximum  with  a  record  of  five  years  of  very 
full  bloom.  These  years  were  1902  and  1904,  preceded,  separated,  and 
followed  by  years  of  scant  bloom;  1912,  preceded  by  a  year  of  scant 
bloom  and  followed  by  a  year  of  moderate  bloom ;  and  1914  and  1916 
with  a  year  of  no  bloom  between.  The  years  1906  to  1911  were  repre- 
sented by  four  years  of  bloom  sufficient  for  a  crop,  one  with  insufficient 
and  one  with  no  bloom.  Thus  for  the  sixteen  years,  ten  had  sufficient 
bloom  and  six  were  deficient  in  bloom. 

There  are  wide  differences  in  varieties  with  regard  to  their  bloom- 
ing tendencies.  Some  varieties  are  inclined  to  produce  sufficient  bloom 
nearly  every  year  while  others  rarely  attain  satisfactory  production. 
Borsdorfer,  as  already  mentioned,  stood  alone  writh  record  of  sufficient 
bloom  in  each  of  the  sixteen  years.  Then  there  were  five  varieties — 
namely,  Arabian,  Berry,  Osimoe,  Rome,  and  Zuzoff — each  with  de- 
ficiency in  only  one  year,  and  six  varieties — Arkansas,  Borsdorf, 
Grandmother,  Hargrove,  Twenty  Ounce,  and  Yellow  Siberian  Crab — 


1924}  BLOOMING  PERIODS  OF  APPLES  135 

each  with  two  of  the  sixteen  years  recorded  as  deficient  in  bloom.  In 
another  group  of  eleven  varieties  including  Fameuse,  Golden  Ball, 
Roe 's  Tolman,  Wolf  River,  and  Wythe,  each  variety  divided  equally 
between  years  of  sufficient  bloom  and  years  of  deficiency.  In  still 
another  group  of  twenty-two  varieties  each  had  from  nine  to  fourteen 
years  of  deficiency,  with  two  to  seven  years  of  sufficient  bloom ;  among 
these  were  Huntsman,  Jefferis,  and  Yellow  Sweet,  each  with  eleven 
lean  years  and  five  full  years ;  Blackwood,  Bogdanoff,  Red  Aport,  and 
three  others  stood  ten  poor  to  six  good.  Most  persistently  unproduc- 
tive of  bloom  were  Peach  and  Rambank  Gasser,  each  with  record  of 
fourteen  years  of  deficient  or  no  bloom  and  only  two  years  with  enough 
bloom  to  promise  a  crop. 

It  is  possible  to  pick  out,  here  and  there  in  the  record,  instances  of 
the  alternation  of  full  or  heavy  with  light  or  no  bloom,  but  occurrence 
of  these  instances  is  extremely  irregular  and  much  less  common  than 
the  occurrence  of  three  to  five  and  even  six  consecutive  years  charac- 
terized by  the  same  degree  of  bloom,  either  moderate  or  full  or  scant. 

In  this  fact  is  seen  evidence  of  the  inequality  of  response  by  dif- 
ferent varieties  to  the  same  attendant  conditions.  Thus  for  the  four 
years  1909  to  1912,  Borsdorf  and  Borsdorfer  bloomed  full  in  each  of 
the  years,  while  Fameuse  had  scant  bloom  in  the  first  three  years  and 
moderate  bloom  in  the  last,  Garden  scant  bloom  in  the  first  three  years 
and  moderate  bloom  in  the  last,  Jefferis  and  Kruder  scant  bloom  in  all 
four  years,  and  so  they  vary  thruout  the  list.  Each  variety  appears  to 
follow  a  course  of  its  own.  Individuality  stands  out  strongly  and  there 
appears  no  single  agency  nor  group  of  agencies  that  operates  on  more 
than  very  restricted  lists  of  varieties  for  limited  periods,  to  govern  per- 
formance in  flower  production. 

Distribution  of  varieties  in  regard  to  amount  of  bloom  in  the  dif- 
ferent years  is  given  in  Table  3.  Arranging  the  same  records  to  bring 
the  varieties  into  two  groups  on  the  basis  of  deficient  or  no  bloom,  and 
sufficient  for  a  crop,  and  adding  the  percentages  in  each  group  for  each 
year,  the  numbers  of  varieties  distribute  as  shown  in  Table  4. 

For  the  sixteen  years  the  average  percentage  of  varieties  having 
bloom  sufficient  for  a  crop  was  62.5  and  there  was  equal  division  of  the 
years,  eight  falling  below  the  average  and  eight  ranging  above,  but 
with  no  regular  order  nor  alternation.  The  years  falling  below  average 
were  1901,  1902,  1905,  1907,  1908,  1909,  1911,  and  1912 ;  those  above 
average  were  1903,  1904,  1906,  1910,  1913,  1914,  1915,  and  1916. 

Effort  has  been  made  to  trace  a  relationship  between  the  amount 
of  bloom  in  any  given  year  and  conditions  of  temperature  and  mois- 
ture prevailing  during  the  period  of  bud  formation — that  is  to  say, 
during  the  months  of  June,  July,  and  August  of  the  preceding  year — 


136 


BULLETIN  No.  251 


[May, 


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No.  of  varieties  
Percentage  

No.  of  varieties  
Percentage  

19S4]  BLOOMING  PERIODS  OF  APPLES  137 

but  the  irregularities  found  were  such  as  to  render  doubtful  the  exist- 
ence of  any  definite  relation. 

The  summer  months  of  1912,  preceding  the  year  with  the  maximum 
percentage  (95.28)  of  varieties  having  sufficient  bloom  (1913),  had  a 
mean  monthly  temperature  of  71°  and  rainfall  of  7.63  inches.  Next 
to  1913  was  1915,  with  91.51  percent  of  the  varieties  having  sufficient 
bloom.  For  the  summer  of  the  preceding  year,  the  mean  monthly  tem- 
perature was  78.2°,  the  highest  of  any  year,  and  the  rainfall  6.49  inches. 

Record  of  these  years  suggests  the  possibility  of  high  percentages 
of  varieties  having  abundant  bloom  in  years  following  high  summer 
temperatures  and  low  rainfall;  but  other  years  with  preceding  sum- 
mer temperatures  almost  as  high  and  with  rainfall  higher,  but  still 
below  normal,  do  not  exhibit  the  same  high  percentages  of  varieties 
with  ample  bloom.  Thus  1911  with  only  41.51  percent  of  the  varieties 
having  sufficient  bloom,  had,  in  the  preceding  summer,  a  mean  monthly 
temperature  of  71.8°  and  a  rainfall  of  8.37  inches ;  1907,  with  38.68 
percent  of  the  varieties  with  bloom  enough  for  a  crop,  had,  for  the 
preceding  summer  period,  72.5°  as  the  mean  monthly  temperature  and 
a  rainfall  of  9.81  inches. 

Perhaps  the  irregularities  of  the  relation  between  the  amount  of 
bloom  and  the  weather  conditions  for  the  preceding  summers  are 
rendered  most  evident  by  grouping  and  comparing  the  highest  and 
lowest  percentages  of  varieties  having  sufficient  bloom.  Thus  the 
average  percentage  of  varieties  having  ample  bloom  in  the  years  1904, 
1913,  and  1915  (90.88  percent)  may  represent  the  highest.  The 
average  mean  monthly  temperature  for  the  preceding  summers  was 
73.3°  and  the  average  rainfall  for  the  same  periods,  8.05  inches.  With 
this  group  compare  the  years  1901,  1902,  and  1907,  the  three  years 
having  the  lowest  percentages  of  varieties  with  sufficient  bloom,  and 
which  have  an  average  of  39.31  percent.  Mean  monthly  temperature 
for  preceding  summers  averaged  73.9°,  with  the  average  rainfall  11.31 
inches. 

While  it  appears  that  the  percentage  of  varieties  having  enough 
bloom  for  a  crop  was  nearly  2%  times  greater  for  the  high  than  for 
the  low  group,  the  average  temperature  for  the  summers  preceding  the 
years  of  high  percentages  of  varieties  having  enough  bloom  was  less 
by  0.6°  than  for  the  same  periods  preceding  percentages  in  the  low 
years,  and  the  rainfall  for  summers  preceding  high  percentages  was 
less  by  3.26  inches  than  for  summers  preceding  low  percentages. 

Comparison  in  the  same  way  may  also  be  made  on  the  basis  of 
highest  and  lowest  rainfall  during  preceding  summers.  Thus  the 
average  rainfall  for  the  summer  months  of  1902,  1907,  and  1915,  the 
years  of  greatest  rainfall,  was  18.71  inches;  and  the  average  per- 
centage of  varieties  with  sufficient  bloom  in  the  next  following  years, 


138  BULLETIN  No.  251  [May, 

1903,  1908,  and  1916,  was  66%  percent.  The  years  1909,  1912,  and 
1914,  following  the  years  of  lowest  rainfall  (an  average  of  5.28  inches 
for  the  summer  months)  show  an  average  of  only  58.81  percent  of  the 
varieties  with  sufficient  bloom.  From  these  contrasting  periods  it 
would  appear  that  the  highest  bloom  percentages  follow  years  of  high- 
est rainfall. 

Again  comparison  may  be  made  on  the  basis  of  mean  temperatures 
for  preceding  summers.  The  three  years  having  highest  summer  tem- 
peratures were  1901,  1913,  and  1914,  with  an  average  monthly  mean 
of  76.5° ;  the  average  of  varieties  having  sufficient  bloom  in  the  next 
following  years  was  65.41  percent.  Years  having  lowest  summer  tem- 
peratures were  1903,  1904,  and  1915,  with  an  average  monthly  mean 
for  the  period  of  70.6° ;  for  the  next  succeeding  years,  1904,  1905,  and 
1906,  the  average  of  varieties  with  sufficient  bloom  was  69.18  percent. 
Here  the  years  of  high  summer  temperatures  were  followed  by  lower 
percentages  of  varieties  having  sufficient  bloom  than  any  recorded  for 
years  following  low  summer  temperatures.  These  comparisons  of  high 
and  low  temperatures  make  it  appear  that,  on  the  basis  of  percentages 
of  trees  having  sufficient  bloom,  high  percentages  follow  years  having 
slightly  lower  temperatures  and  appreciably  lower  rainfall  than  the 
years  preceding  the  low  percentage  years ;  that  on  the  basis  of  rainfall, 
high  percentages  of  varieties  with  sufficient  bloom  follow  years  of 
highest  rainfall ;  and  that  on  the  basis  of  temperature,  the  high  per- 
centages follow  the  lowest  temperatures. 

Several  other  combinations  have  been  examined,  but  no  importance 
attaches  to  any  of  them.  Correlation  between  percentages  of  bloom 
and  temperatures  and  rainfall  of  preceding  years  cannot  be  established 
for  the  reason  that  temperature  and  rainfall  are  only  two  of  a  long 
array  of  climatic  factors,  all  of  which  operate  to  influence  bloom  per- 
formance. 

Temperature  and  rainfall  may  be  the  most  important  agencies 
affecting  amount  of  bloom,  but  taken  separately  they  cannot  lead  to 
correct  interpretation  of  observed  results  because  other  and  possibly 
equally  important  factors  are  left  out.  Computations  from  incomplete 
data  only  serve  to  confuse ;  they  do  not  aid  in  understanding  observed 
phenomena  and  hence  accomplish  no  good  purpose. 

That  the  wide  variations  in  numbers  of  varieties  producing  bloom 
and  the  equally  wide  variations  in  amount  of  bloom  in  different  years, 
result  from  definite  causes  is  a  warranted  assumption,  but  determina- 
tion of  these  causes  is  impossible  in  the  absence  of  complete  data,  and 
even  with  full  data  would  be  difficult  because  of  the  complex  nature  of 
the  problem.  Like  any  other  problem  involving  the  physiological 
processes  of  plants,  the  factors  that  influence  results  are  very  nu- 
merous ;  these  factors  interact  among  themselves,  they  are  difficult  to 


1924}  BLOOMING  PERIODS  OF  APPLES  139 

isolate;    and  to  correctly  associate  any  one  of  them  with  observed 
phenomena  is  possible  only  thru  close  and  prolonged  study. 

AMOUNT  OF  BLOOM  AND  DISTRIBUTION  OF  VARIETIES 
INTO  TIME-GROUPS 

An  impression,  acquired  from  observations  and  unclassified  notes, 
that  concentration  of  the  flowering  of  varieties  into  a  few  time-groups 
occurred  in  years  of  heavy  bloom,  and  that  wide  distribution  into  many 
groups  was  characteristic  of  years  of  light  bloom,  is  not  fully  supported 
by  the  tabulated  records  of  all  years.  It  is  true  that  1907,  the  year  of 
widest  distribution,  when  there  were  fifteen  groups  ranging  from  three 
to  seventeen  days,  was  one  of  two  years  having  the  minimum  amount 
of  bloom.  In  1907  only  41,  or  38.68  percent,  of  the  106  varieties  had 
bloom  in  quantity  sufficient  to  promise  a  crop ;  37  of  the  varieties  were 
recorded  as  having  moderate  bloom  and  4  as  having  full  bloom;  21 
varieties  had  no  bloom  and  44  had  each  a  few  scattering  flowers,  not 
enough,  however,  to  suggest  a  crop  of  fruit.  The  year  of  maximum 
concentration,  when  the  varieties  having  bloom  enough  for  a  crop  were 
gathered  into  three  groups  of  four-,  five-,  and  six-day  periods,  was 
1915,  a  year  standing  next  below  the  maximum  in  amount  of  bloom. 
In  this  year  there  were  97  varieties,  or  91.51  percent  of  the  total,  with 
bloom  sufficient  for  a  crop ;  47  varieties  had  moderate  bloom,  50 
bloomed  full  and  22  of  these  were  very  full. 

These  years  of  minimum  and  near-maximum  bloom  support  the  im- 
pression of  a  relationship  between  amount  of  bloom  and  time  distribu- 
tion, but  this  suggested  relationship  is  rendered  doubtful  by  the  bloom 
performance  of  other  years.  For  the  year  of  maximum  bloom,  1913, 
when  95.28  percent  of  the  varieties  carried  bloom  enough  for  a  crop, 
there  was  distribution  into  eight  groups  ranging  from  four  to  eleven 
days.  In  the  year  1902  which,  in  company  with  the  year  1907,  records 
the  lowest  percentage  of  bloom,  only  38.68  percent,  there  was  con- 
centration into  four  groups  ranging  from  five  to  eight  days.  Next 
above  the  minimum  in  amount  of  bloom  was  the  year  1901,  with  a  per- 
centage of  40.57  and  with  five  groups  ranging  from  four  to  eight  days. 
The  three  years  1905,  1908,  and  1909,  each  with  a  distribution  of 
varieties  in  eleven  groups,  have  percentages  of  varieties  blooming  of 
50,  60.38,  and  52.83  respectively.  Without  going  further  into  detail 
it  appears  that  for  selected  pairs  of  years  a  rather  definite  relation 
may  be  shown  between  the  number  of  varieties  blooming  and  the  dis- 
tribution of  the  varieties  into  greater  or  less  numbers  of  time-groups, 
but  when  the  aggregate  of  records  is  considered  no  constant  relation 
is  apparent. 


140  BULLETIN  No.  251  [May, 

TEMPERATURE  AND  DISTRIBUTION  OP  BLOOM 

Temperature  for  the  duration  of  the  blooming  period  is,  without 
doubt,  an  important  factor  in  influencing  distribution  of  varieties  into 
groups  representing  flowering  periods  of  different  lengths.  Comparing 
the  record  of  flowering  periods  and  distribution  with  the  mean  daily 
temperatures  for  the  respective  years,  it  appears  that  in  the  main, 
length  of  period  and  distribution  fluctuate  with  mean  daily  tempera- 
tures. Thus  the  year  1915,  with  the  shortest  recorded  full  flowering 
period  of  ten  days  and  concentration  of  the  100  varieties  into  four-, 
five-,  and  six-day  groups,  had  a  mean  daily  temperature  for  the  period 
April  23  to  May  2  of  67.1° ;  while,  the  year  1907,  with  a  flowering 
period  of  twenty-two  days  and  a  distribution  of  the  82  varieties  into 
fifteen  time-groups  ranging  in  lertgth  from  three  to  seventeen  days, 
had  a  mean  daily  temperature  fojPihe  period  April  20  to  May  11  of 
48.1°.  Other  years  exhibit  a  somiglfchat  similar  relation,  but  there  are 
sufficient  irregularities  to  indicate"  that  factors  other  than  temperature 
frequently  operate  to  modify  botlf  length  of  blooming  period  and  range 
of  distribution.  For  example,  the. year  1910,  with  a  full  flowering 
period  of  eighteen  days  and  a  dislribution  of  varietal  periods  into  six 
groups  of  four  to  nine  days  each,  tifid  a  mean  daily  temperature  for  the 
period  April  2  to  April  19  of  53.J^^^tiile  for  the  year  1914,  with  a 
full  period  of  fifteen  days  and  the  »|ietal  periods  distributed  in  nine 
groups  of  five  to  thirteen  days  each^he  mean  daily  temperature  from 
April  27  to  May  11  was  61.5°. 

A  further  indication  of  the  operation  of  factors  other  than  tem- 
perature is  suggested  in  the  fact  that  varietal  flowering  periods  of 
three  days  are  recorded  only  in  the  years  1905,  1907,  1908,  and  1909, 
all  of  which  had  long  full-flowering  periods.  The  distribution  of 
varieties  into  the  maximum  numbers  of  groups  and  mean  daily  tem- 
peratures for  the  respective  flowering  periods  were  as  follows:  58.4°, 
48.1°,  50.4°,  and  55.6°. 

Examination  of  the  flowering  record  of  all  varieties  arranged  by 
years  shows  that  wide  variation  in  length  of  varietal  blooming  periods 
in  different  years  is  common  to  all,  but  the  range  varies  for  different 
varieties.  There  are  8  varieties  each  having  three  days  as  the  mini- 
mum period  ;  for  these  varieties  the  maxima  range  from  eight  to  fifteen 
days.  Next  to  this  is  a  group  of  63  varieties,  each  with  a  minimum 
period  of  four  days  and  here  the  maxima  range  from  eight  to  sixteen 
days.  Then  follows  a  group  of  33  varieties  each  with  a  minimum  of 
five  days  and  maxima  ranging  from  nine  to  seventeen  days.  Finally, 
of  2  varieties  each  having  a  six-day  period  as  the  minimum,  one  has  a 
maximum  period  of  eleven  days,  the  other  a  maximum  period  of  fifteen 
days. 

Variation  in  length  of  flowering  period  is  expected.  Mean  tem- 
peratures for  particular  periods  vary  greatly  in  different  years,  and 


BLOOMING  PERIODS  OF  APPLES  141 

flowering  periods  should  be  long  when  temperatures  are  low  and  short 
when  they  are  high. 

While  this  relation  between  temperatures  and  length  of  flowering 
periods  is  apparent  in  a  general  way,  there  are  many  irregularities  and 
such  wide  departures  from  the  rule  as  to  make  it  evident  that  impor- 
tant and  complex  factors  other  than  temperature  and  atmospheric  con- 
ditions at  time  of  blooming,  operate  to  modify  the  duration  of  flower- 
ing periods.  To  illustrate,  the  flowering  periods  of  Domine  and 
Fameuse  for  the  year  1907  may  be  compared.  The  period  for  Domine 
was  six  days,  that  for  Fameuse  fourteen  days;  the  mean  daily  tem- 
perature for  the  six-day  period  of  Domine  was  47.6°,  that  for  the 
fourteen-day  period  of  Fameuse  47.4°.  It  does  not  appear  reasonable 
that  a  difference  of  0.2°  in  mean  daily  temperature  should  be  the  sole 
cause  of  prolongation  of  one  period  to  2%  times  the  length  of  the  other. 

A  similar  case  appears  in  the  record  of  flowering  periods  for  Rome 
and  Wolf  River  in  1903.  The  mean  daily  temperature  for  the  Rome 
period  of  twelve  days  was  53.6°,  and  for  the  five-day  period  of  Wolf 
River  53.4°.  Another  example  is  found  in  comparison  of  the  records 
of  Shockley  and  Tolman,  also  for  the  year  1903.  Shockley  had  a  flower- 
ing period  of  ten  days,  Tolman  a  flowering  period  of  six  days ;  the 
mean  daily  temperature  for  the  Shockley  period  was  50.5°,  that  for  the 
Tolman  period  49.6°.  Here  the  shorter  period  had  a  mean  daily  tem- 
perature less  by  0.9°  than  that  of  the  longer  period.  For  the  year  1908 
these  same  varieties  show  a  rather  extreme  difference ;  Shockley  had  a 
flowering  period  of  six  days  while  that  of  Tolman  was  sixteen  days, 
but  in  this  case  temperature  may  be  accepted  as  the  chief  cause  of 
difference,  for  the  mean  daily  temperature  of  the  Shockley  period  was 
57.6°,  while  that  for  the  Tolman  period  was  47.1°,  a  difference  of 

101/20. 

INCONSTANCY  OF  RELATIVE  LENGTHS  OP  VARIETAL 
BLOOMING  PERIODS 

With  nearly  all  varieties  there  are  marked  irregularities  in  the 
alternation  of  long  and  short  blooming  periods  and,  further,  there  are 
conspicuous  departures,  from  those  relative  lengths  of  periods  of  dif- 
ferent varieties,  that  might  be  easily  assumed  to  be  constant ;  that  is 
to  say,  where  two  varieties  in  any  one  year  have  blooming  periods  dif- 
fering in  length  by  several  days,  one  perhaps  twice  as  long  as  the  other, 
it  would  not  be  unreasonable  to  suppose  that  the  varieties  in  question 
would  hold  to  an  approximation  of  the  difference  in  other  or  all 
seasons.  As  a  matter  of  fact,  the  relative  lengths  of  the  periods  in  one 
season  may  bo  reversed  in  a  succeeding  season.  Such  occurrence  indi- 
cates plainly  that  temperature  and  general  atmospheric  conditions, 
which  are  commonly  regarded  as  the  chief  determiners  of  length  of 
blooming  periods,  do  not  act  equally  on  all  varieties  in  all  seasons,  or 


142  BULLETIN  No.  251  [May, 

that  varieties  develop  within  themselves  qualities  that  render  them  less 
susceptible  to  stimulation,  or  more  resistant  to  adverse  conditions  in 
one  season  than  in  another.  Records  for  Tolman  and  Whitney  will 
serve  to  illustrate  the  fluctuations  here  referred  to.  The  flowering 
period  for  Tolman  in  1903,  a  year  having  a  long  average  flowering 
period  (9.2  days)  for  all  varieties,  was  six  days;  while  in  1908,  when 
the  average  period  for  all  varieties  was  short  (5.94  days),  the  period 
recorded  for  Tolman  was  sixteen  days.  In  contrast  with  this  record 
Whitney,  with  an  average  flowering  period  for  sixteen  years  of  7% 
days,  had  its  flowering  period  lengthened  to  fourteen  days  in  1903  and 
contracted  to  five  days  in  1908.  Records  for  these  two  varieties  for  the 
two  years,  placed  side  by  side  for  ready  comparison,  appear  as  follows : 

1903  1908 

Blooming  period  for  Tolman 6  days         16  days 

Blooming  period  for  Whitney 14  days          5  days 

Tolman  did  not  bloom  in  1907,  so  that  the  two  varieties  can  be 
compared  for  only  fifteen  years.  For  the  years  other  than  the  two 
given  above,  the  flowering  periods  of  the  two  varieties  were  as  follows : 
they  were  equal  in  1912,  in  five  years  Tolman  had  the  longer  periods 
by  one  to  two  days,  and  in  seven  years  Whitney  had  the  longer  periods 
by  one  to  five  days.  The  trees  compared  were  of  the  same  age,  grew 
but  a  few  rods  apart  and  received  the  same  care  each  year. 

To  further  illustrate  irregularities  in  flowering  periods,  certain 
other  varieties  may  be  briefly  mentioned.  Ben  Davis  is  recorded  as 
having  a  range  in  length  of  periods  of  five  days  to  thirteen  days,  dis- 
tributed as  follows:  five-day  periods  in  each  of  five  years,  six-day 
periods  in  each  of  four  years,  seven-day  periods  in  each  of  two  years, 
eight-day  periods  in  each  of  two  years,  and  thirteen-day  periods  in  each 
of  two  years.  The  two  thirteen-day  periods  are  recorded  for  the  years 
1907,  in  which  the  average  blooming  period  for  all  varieties  was  9.93 
days,  and  1914,  in  which  the  average  blooming  period  for  all  varieties 
was  9.03  days.  The  mean  daily  temperature  for  the  blooming  period 
in  1907  was  49.4°,  in  1914  it  was  60.4° ;  a  difference  of  11°,  altho  the 
blooming  periods  were  the  same.  For  the  five  years  having  each  a  five- 
day  period,  the  mean  daily  temperatures  for  the  bloomirig  periods 
range  from  47.4°  in  1908  to  70.2°  in  1913;  an  extreme  difference  of 
22.8°. 

The  record  for  Domine  shows  equal  flowering  periods  of  six  days 
for  the  years  1906  and  1907,  with  a  difference  of  14.3°  between  the 
mean  daily  temperatures  of  the  periods  for  the  two  years.  Similarly 
the  years  1903  and  1904  had  each  an  eight-day  period  with  a  difference 
between  mean  daily  temperatures  of  10°. 

Variations  in  length  of  blooming  period  and  relations  to  mean  daily 
temperatures  such  as  have  been  cited  are  of  common  occurrence  in  all 


1924]  BLOOMING  PERIODS  OF  APPLES       .  143 

varieties,  but  are  more  strikingly  in  evidence  in  some  varieties  than 
in  others. 

The  variations  indicate  clearly  that  there  are  more  influences  con- 
trolling length  of  blooming  period  than  can  be  ascribed  to  spring 
weather  conditions  alone,  and  by  their  marked  irregularity  suggest 
that  the  individual  rather  than  the  variety  must  be  the  basis  from 
which  performance  is  considered.  Trees  of  one  variety  growing  to- 
gether in  a  single  row  do  not  act  alike;  one  starts  earlier,  pushes 
stronger,  and  completes  its  period  of  bloom  in  less  time  than  does  its 
neighbor.  It  is  said  of  such  a  tree  that  it  was  in  better  condition  than 
the  other,  had  more  vigor,  and  thus  was  enabled  to  outclass  its  neigh- 
bor. This  is  true,  but 'when  the  question  is  asked  as  to  why  the  tree 
was  in  better  condition  and  possessed  of  greater  vigor,  the  answer  is 
not  immediately  forthcoming. 

The  two  trees,  Tolman  and  Whitney,  had  been  neighbors  for  several 
years,  subjected  to  identical  conditions  so  far  as  is  now  apparent.  It 
is  necessary  to  go  back  several  months  or  possibly  years,  investigate 
relative  activity  in  the  various  life  processes,  determine  the  perfor- 
mance, and  then  possibly  fail  to  find  the  existing  cause  or  causes  of  the 
differences  recorded.  The  tree  of  greater  vigor  may  be  constitutionally 
better  than  its  neighbor,  it  may  have  had  access  to  better  food  supply, 
it  may  have  more  completely  recovered  from  a  fruiting  effort,  it  may 
not  have  been  exhausted  by  fruit  production  the  year  previous  while 
its  less  vigorous  neighbor  may  have  been,  or  it  may  have  escaped  a 
parasite  that  damaged  its  neighbor.  Any  of  these  or  other  possible 
causes,  singly  or  in  combination,  may  have  operated  to  bring  about  the 
recorded  difference,  leaving  no  evidence  of  operation  that  is  apparent 
at  the  time  bloom  record  is  made. 


144  BULLETIN  No.  251  [May, 

SUMMARY 

Blooming  marks  what  is  perhaps  the  most  critical  period  in  the  pro- 
duction of  a  fruit  crop,  and  success  or  failure  of  the  crop  is,  in  a  large 
measure,  dependent  upon  spring  weather  conditions.  Blooming  rec- 
ords of  106  varieties,  each  having  a  record  of  ten  to  sixteen  years,  are 
considered  for  the  sixteen-year  period  1901-1916.  Record  for  each 
variety  for  each  year  includes  dates  of  first  bloom,  full  bloom,  and 
petals  falling ;  also,  an  estimate  of  the  amount  of  bloom. 

1.  Flowering  periods  in  Illinois  are  extremely  variable  from  year 
to  year,  but  in  general  are  shorter  than  flowering  periods  in  Virginia, 
New  York,  Oregon,  and  in  England. 

2.  For  the  sixteen  years  the  full  flowering  period  for  all  varieties 
has  ranged  from  ten  to  twenty-two  days,  with  an  average  of  approxi- 
mately sixteen  days.    The  earliest  date  of  an  open  flower  was  April 
2 ;  the  latest  date  in  the  record  of  petals  falling  was  May  21,  placing 
the  extremes  for  the  sixteen  years  fifty  days  apart. 

3.  Early  Ripe,  Zuzoff,  and  Oldenburg,  while  shifting  relative  posi- 
tions from  year  to  year,  hold  place  as  the  earliest  bloomers  more  con- 
sistently than  do  other  varieties.     The  latest  blooming  varieties  weue 
Repka  Malenka  and  Wythe. 

4.  The  blooming  period  in  1910  was  a  full  month  earlier  than  in 
other  years  because  of  abnormally  high  temperatures  during  the  month 
of  March. 

5.  Blooming  periods  for  individual  varieties  have  varied  in  length 
between  three  and  seventeen  days,  while  average  periods,  for  all  years, 
range  from  five  to  ten  days.    The  average  period  for  all  varieties  was 
five  days  in  1901  and  1915 ;  six  days  in  each  of  two  years,  seven  days 
in  each  of  six  years,  eight  days  in  each  of  three  years,  nine  days  in 
1903  and  1914,  and  ten  days  in  1907. 

6.  Extremes  in  length  of  blooming  periods  for  individual  varieties 
may  be  near  together  in  one  year  and  widely  separated  in  another 
year.     Thus  in  1907  the  shortest  period  was  three  days,  the  longest 
seventeen  days,  and  each  number  of  days  between  three  and  seventeen 
was  represented  by  1  to  13  varieties,  giving  fifteen  time-groups  for  that 
year,  while  in  1915  there  was  concentration  into  three  groups  of  four-, 
five-,  and  six-day  periods. 

7.  Amount  of  bloom  was  estimated  for  each  variety  for  each  year 
and  from  this  record  it  appears  that  68  varieties  aggregate  151  records 
of  no  bloom.    For  the  full  list  of  varieties  there  are  485  records  of 
bloom  insufficient  for  a  crop,  and  1,060  records  of  a  sufficient  amount 
or  an  excess  of  bloom.    In  other  words,  621/2  percent  of  the  records  in- 
dicate enough  bloom  and  37 1/2  percent  represent  deficiencies.   Records 
of  very  full  or  excess  bloom  aggregate  only  92,  or  5.42  percent  of  all 


l'J24\  BLOOMING  PERIODS  OF  APPLES  145 

records,  and  these  are  distributed  in  eight  of  the  sixteen  years.  Effort 
to  establish  a  relationship  between  amount  of  bloom  and  temperature 
and  moisture  conditions  prevailing  during  the  period  of  bud  forma- 
tion in  preceding  summers  developed  such  irregularities  as  to  render 
the  existence  of  any  definite  relation  doubtful. 

8.  In  a  general  way  mean  temperatures  during  blooming  periods 
influence  the  length  of  periods  and  the  distribution  of  varieties  into 
few  or  many  time-groups,  but  there  are  enough  irregularities  to  indi- 
cate plainly  that  there  are  influences  other  than  temperature  that 
operate  to  modify  both  length  of  period  and  range  of  distribution  of 
varieties. 

9.  Inconstancy  in  relative  lengths  of  blooming  periods  is  charac- 
teristic of  all  varieties.    Two  varieties,  one  having  a  blooming  period 
twice  as  long  as  the  other  in  a  particular  year,  may  exactly  reverse 
their  relative  positions  in  a  succeeding  year. 

10.  Influences  affecting  the  blooming  periods  of  apple  trees  are 
extremely  complex.    Climatic  conditions  are  important,  but  their  in- 
fluence is  modified  by  physiological  characteristics  which  are  obscure, 
difficult  to  isolate,  and  which  operate  to  make  it  impossible  to  interpret 
the  vagaries  of  blooming  phenomena  from  the  bloom  record  alone. 


UNIVERSITY  OF  ILLINOIS-URBANA 


